Global warming and the earlier start of the Japanese-cedar (Cryptomeria japonica) pollen season in Toyama, Japan

Atmospheric pollen surveys were conducted in Toyama City, Japan over a 21-year period (1983–2003). Airborne pollen was collected by two methods, the gravimetric method and the volumetric method. The gravimetric method indicated that the start of the Cryptomeria japonica pollen season, as indicated by pollen dispersion, has advanced from day 73 (from January 1) in 1983 to day 47 in 2003. Measurements taken using the volumetric method confirmed this trend. There was a significant correlation between the start dates obtained by both methods. Meteorological data indicated that the most noticeable elevation in temperature during the experimental period occurred in February – an increase of 2.1°C. Significant correlations existed between the mean temperatures and the start dates of the pollen season. These results support the steadily increasing number of reports indicating a global warming trend. The temperature change in February in affecting the start dates of the C. japonica pollen season is particularly relevant in the context of human health. Further studies will be needed to clarify the effects of the global warming trend on the pollen season and human health in more detail.     

The pollen season dynamics and the relationship among some season parameters (start,end, annual total,season phases) in Kraków,Poland, 1991–2008

The dynamics of 15 taxa pollen seasons in Kraków, in 1991–2008 was monitored using a Burkard volumetric spore trap of the Hirst design. The highest daily pollen concentrations were achieved in the first half of May, and they were caused mainly by Betula and Pinus pollen. The second period of the high concentrations took place from the middle of July to the end of August (mainly Urtica pollen). Tree pollen seasons were shorter (18–24 days) in comparison with the most herbaceous pollen seasons (73–89 days), except at Artemisia and Ambrosia seasons (30 and 24 days, respectively). The season phases (percentyles) of the spring and late-summer taxa were the most variable in the consecutive years. The highest annual sums were noted for Urtica, Poaceae (herbaceous pollen seasons) and for Betula, Pinus, Alnus (tree pollen seasons), and the highest variability of annual totals was stated for Urtica, Populus, Fraxinus and the lowest for Ambrosia, Corylus, Poaceae. For the plants that pollinate in the middle of the pollen season (Quercus, Pinus and Rumex), the date of the season start seems not to be related to the season end, while for late pollen seasons, especially for Ambrosia and Artemisia, the statistically negative correlation between the start and the end season dates was found. Additionally, for the most studied taxa, the increase in annual pollen totals was observed. The presented results could be useful for the allergological practice and general botanical knowledge.     

An aeropalynological study of metropolitan Toronto

This study uses 6 years of atmospheric pollen data to examine temporal variability of airborne pollen concentrations at various scales. Airborne pollen was collected from 1985 to 1990 with a Burkard trap, located 18 m above ground at Scarborough College, Toronto, Canada. Pollen season parameters are defined and summarized for all taxa in preparation for developing forecasting models. Annual totals of pollen concentration show great interannual variability. The highest coefficient of variation occurs inTsuga, Fraxinus, Betula andFagus, while the lowest inQuercus andAmbrosia. Some taxa show periodic cycles consistent with mast reproductive behaviour. In many studies, the start of the pollen season is defined as an arbitrary percentage of the annual sum. As a result, the start of the season cannot be identified until the season has passed. As well, due to large fluctuations in annual sum, start dates are more variable. This is not practical for the purposes of forecasting. In this study, the start of the pollen season is defined by a critical concentration threshold which signals the onset of the main pollen season in all years. These critical levels ranged from 2 to 60 grains/m³ for the abundant taxa. Interannual variation in the start of the season is approximately 20 days for tree taxa, 5 days for Poaceae, and 2 days forAmbrosia. For many plants, dehiscence is triggered at a critical level of accumulated degree-days. Since annual rates of temperature increase show great variation, there is also interannual variability in the onset of pollen release. Multi-year average pollen curves incorporate these differences in onset and may give an inaccurate representation of the pollen season in a typical year. This paper presents a method of aligning yearly pollen curves to reduce seasonal variation and more accurately represent both the average timing and magnitude of the pollen season. For some types, such asBetula and Poaceae, the resulting curves are positively skewed. Tree taxa, in general, exhibit a more symmetric pollen concentration curve. Aligned average pollen concentration curves are presented for Toronto in the form of a pollen calendar. In addition, phenological data for all common taxa are summarized.     

EFFECTS OF DISTANCE BETWEEN POLLEN DONOR AND POLLEN RECIPIENT ON FITNESS COMPONENTS IN ESPELETIA SCHULTZII

The effect of flowering time and of distance between pollen donor and pollen recipient on the proportion of filled achenes, aborted seeds, and seedling survivorship was studied in populations of Espeletia schultzii in the Venezuelan Andes. Hand-pollinations were performed in two different years and at different times during the flowering season. Pollinations within-population included crosses between plants within a few meters to a maximum of 500 m apart and between-population pollinations included crosses between plants more than 10 km and up to 78 km away. Late in the flowering season, plants suffered a reduction in the proportion of filled achenes and an increase in aborted seeds. The proportion of filled achenes and aborted seeds did not vary significantly between the distances between pollen and ovules in crosses done early in the flowering season. However, the proportion of filled achenes in crosses between individuals within 30 m distance were very variable, either very successful or not successful. Beyond 30 m, for some of the populations, the frequency of unsuccessful crosses was almost 0. This pattern was observed at three elevation sites in two consecutive years. When crosses were done late in the flowering season, the proportion of filled achenes was lower in crosses between close individuals and between very distant ones. Seedling survivorship varied significantly between the crossing distances at the higher elevation only. The results show that a clear effect of the incompatibility alleles on the crossing success of the plants is present in the different populations examined, while they suggest that the effect of inbreeding or outcrossing depression is less clear but might still be present only under certain conditions. Late in the season, when plants might have fewer resources available for reproduction and at the high and intermediate site where cold and dry environmental conditions are less favorable for the plants, the discrimination among distances was stronger.     

Variations and trends of birch pollen seasons during 15 years (1996–2010) in relation to weather conditions in Poznań (western Poland)

Birch (Betula) pollen seasons were examined in relation to meteorological conditions in Poznań (1996–2010). Birch pollen grains were collected using a volumetric spore trap. An alternate biennial cycle of birch pollen season intensity was noticed in Poznań. The main factors influencing birch pollen season intensity were average daily minimum temperatures during the second fortnight of May and the month of June one year before pollination as well as the intensity of the pollen season of the previous year. Most of the pollen grains are recorded during the first week of the season; the number of pollen grains recorded at this time is positively correlated with mean maximum temperature and negatively correlated with daily rainfall. The significant effect of rainfall in reducing the season pollen index was noticed only during weak pollen seasons (season pollen index <?mean). In addition, mean daily maximum temperature during the first two weeks of the birch pollen season markedly influences its duration. No significant trends in duration and intensity of the pollen season were recorded, however, a slight tendency towards early pollination was observed (?0.4 days/year, p?=?0.310).     

Pinus pollen season trend in South Spain

In Andalusia (southern Spain), Pinus species are found in mountainous areas and nature reserves, though some species are also grown as ornamentals in cities. Annual airborne pollen trends are regarded as an indicator of variations in climate prompted by overall climate change. Airborne pollen concentration also provides a useful tool for analyzing alterations in the distribution of vegetation in response to environmental factors and to changes in land use. The present study analyzed the Pinus pollen season over 22 years (1993–2014) in 4 Andalusian cities (Córdoba, Granada, Jaén, and Málaga), and examined correlations between airborne pollen concentrations and meteorological parameters (temperature and rainfall). Pinus pollen season lasted from March to June, starting first in Málaga and later in eastern Andalusia. Differences between the pollen curves for each city were attributable to differing proportions of pine species in each province. Temperatures during the months prior to flowering tended to fall, prompting delayed onset of the pollen season in most cities. No significant results were observed for rainfall patterns in most cities. Total pollen concentrations increased at most sites, suggesting that the recorded decline in pine-nut output was not influenced by flowering rates, but to the impact of a local pest.     

Non-native <Emphasis Type="Italic">Ambrosia</Emphasis> pollen in the atmosphere of Rzeszów (SE Poland); evaluation of the effect of weather conditions on daily concentrations and starting dates of the pollen season

The investigated problem was whether and to what an extent the elements of weather conditions were associated with changes in the concentration of Ambrosia pollen in air. The study was carried out in the years 1997–2004 using the volumetric method. Ragweed did not occur in the flora of the town of Rzeszów and its vicinity, but every year its pollen occurred at concentrations considerably exceeding the threshold values for the allergic response. The pollen seasons usually began from near the end of August to the first part of September. The values of daily concentrations varied greatly: days without pollen grains being frequently noted while single grains occurred long before and after the season. The effect of the elements of weather on changes in the concentration of pollen in the air was slight. Taking into account all meteorological parameters, it can be stated that an increase in the number of pollen grains is connected with increased temperature and higher wind speeds, but negatively correlated with humidity and rainfall. These relationships can usually be explained by the effects of the type of weather taking place over the wider region. The analysis of the results showed that pollen was probably transported from distant regions. The mean angle at which the greatest pollen concentrations were recorded corresponded to the SE wind direction. The analysis of synoptic phenomena during the pollen season confirms the thesis about the long-distance transport from the south, southeast and southwest. A close dependence was also found between the starting date of the season and the sum of maximum temperatures and the sum of differences between the maximum and minimum temperatures.     

<Emphasis Type="Italic">Cyperaceae</Emphasis> and <Emphasis Type="Italic">Juncaceae</Emphasis> pollination measured in the air at two sites in SW Spain

The presence of airborne Cyperaceae and Juncaceae pollen was quantified using volumetric aerobiological traps over a 10-year period at two sites in SW Spain separated by 60 km (Badajoz 10 years, Mérida 3 years). The Pearson correlation coefficient was calculated between the daily and hourly concentrations. The values of the principal meteorological parameters—temperature, rainfall, relative humidity, and speed and direction of the wind—were calculated during the study period, and with the accumulated values corresponding to the period prior to pollination. The beginning and ending dates and the duration of the main pollen season (MPS) were also analyzed. Even though both families are anemophilous, the presence of their pollens in the air was low. The annual accumulated daily concentrations were in the range 1.8–15.8 for Juncaceae and 111.8–473.9 for Cyperaceae—values far lower than any other anemophilous pollen type. The Cyperaceae pollen concentration peaked between 09:00 and 12:00. The meteorological factor most closely related to its daily variations was found to be the wind direction, showing that location of the sources is of great importance. The results lend support to the hypothesis of a limitation of allogamous reproduction in favour of vegetative multiplication in both families. Nevertheless, the principal source of the airborne Cyperaceae pollen was found to be Scirpus holoschoenus, whose pollen is distinguishable from the rest. Hence, because of its large production of pollen, this species can be characterized as anemophilous and allogamous. Rainfall in the preceding autumn seemed to be responsible for the amount of Cyperaceae pollen in the air, since a lack of rain was found to be associated with lower densities in the traps. For the Juncaceae, it seems that the temperatures of the preceding December constituted the most limiting meteorological parameter.     

Ragweed and mugwort pollen in Szczecin, Poland

Ragweed (genus Ambrosia) and mugwort (Artemisia vulgaris) pollen grains are known to be very potent aeroallergens, often noted to enter into cross reactions. The aim of the study was to analyse ragweed and mugwort pollen release in Szczecin (western Poland) during the period 2000–2003. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90% of the total catch. Of the 4 years studied, the lowest concentration of ragweed pollen was observed in 2000. In 2000, the annual ragweed pollen count was very high, threefold higher than in 2001. There was a high Ambrosia pollen count in 2003, with the highest daily value of 84 grains/m³. The mugwort pollen season started in the third 10-day period of July and lasted to the end of August in all of the years studied. Analysis of pollen deposition from different Szczecin city’s districts showed that the highest exposure to ragweed pollen allergens occurred in the Majowe district, which is related to the presence of numerous plants of Ambrosia in that district. The mugwort pollen deposition was more abundant in the Żelechowa district, which is an area with villas and gardens. Statistically significant correlations were found between the ragweed pollen count in the air and the maximum wind speed, air temperature and relative humidity and between the mugwort pollen count in the air and air temperature and relative humidity.     

The effect of the meteorological factors on the Alnus pollen season in Lublin (Poland)

Alder pollen seasons and the effect of meteorological conditions on daily average pollen counts in the air of Lublin (Poland) were analysed. Alnus pollen grains reach very high concentrations in the atmosphere of this city during the early spring period and the parameters of pollen seasons were very different in the particular years studied. The pollen season lasted on average one month. The highest variation was observed for the peak value and the Seasonal Pollen Index (SPI). The pollen seasons, which started later, had shorter duration. Peak daily average pollen counts and SPI value were higher during the shorter seasons. Similarities in the stages of pollen seasons designated by the percentage method depended on the start date of the pollen season. Season parameters were mainly correlated with thermal conditions at the beginning of the year. Regression analysis was used to predict certain characteristics of the alder pollen season. The highest level of explanation of the variation in Alnus pollen season start and peak dates was obtained in the model using mean temperature in February. The obtained regression models may predict 82% of the variation in the pollen season start date, 73% of the variation in the duration, and 62% in the peak date.     

Effect of meteorological parameters on Poaceae pollen in the atmosphere of Tetouan (NW Morocco)

Poaceae pollen is one of the most prevalent aeroallergens causing allergenic reactions. The aim of this study was to characterise the grass pollen season in Tetouan during the years 2008–2010, to analyse the effect of some meteorological parameters on the incidence of the airborne Poaceae pollen, and to establish forecasting variables for daily pollen concentrations. Aerobiological sampling was undertaken over three seasons using the volumetric method. The pollen season started in April and showed the highest pollen index in May and June, when the maximum temperature ranged from 23 to 27 °C, respectively. The annual pollen score recorded varied from year to year between 2,588 and 5,404. The main pollen season lasted 114–173 days, with peak days occurring mainly in May; the highest concentration reached 308 pollen grains/m³. Air temperature was the most important meteorological parameter and correlated positively to daily pollen concentration increase. An increase in relative humidity and precipitation was usually related to a decrease in airborne pollen content. External validation of the models performed using data from 2011 showed that Poaceae pollen concentration can be highly predicted (64.2–78.6 %) from the maximum temperature, its mean concentration for the same day in other years, and its concentration recorded on the previous day. Sensitive patients suffering allergy to Poaceae pollen are at moderate to highest risk of manifesting allergic symptoms to grass pollen over 33–42 days. The results obtained provide new information on the quantitative contribution of the Poaceae pollen to the airborne pollen of Tetouan and on its temporal distribution. Airborne pollen can be surveyed and forecast in order to warn the atopic population.     

Pollinator preference and pollen viability mediated by flower color synergistically determine seed set in an Alpine annual herb

Gentiana leucomelaena manifests dramatic flower color polymorphism, with both blue‐ and white‐flowered individuals (pollinated by flies and bees) both within a population and on an individual plant. Previous studies of this species have shown that pollinator preference and flower temperature change as a function of flower color throughout the flowering season. However, few if any studies have explored the effects of flower color on both pollen viability (mediated by anther temperature) and pollinator preference on reproductive success (seed set) in a population or on individual plants over the course of the entire flowering season. Based on prior observations, we hypothesized that flower color affects both pollen viability (as a function of anther temperature) and pollen deposition (as a function of pollinator preference) to synergistically determine reproductive success during the peak of the flowering season. This hypothesis was tested by field observations and hand pollination experiments in a Tibetan alpine meadow. Generalized linear model and path analyses showed that pollen viability was determined by flower color, flowering season, and anther temperature. Anther temperature correlated positively with pollen viability during the peak of the early flowering season, but negatively affected pollen viability during the peak of the mid‐ to late flowering season. Pollen deposition was determined by flower color, flowering season (early, or mid‐ to late season), and pollen viability. Pollen viability and pollen deposition were affected by flower color that in turn affected seed set across the peak of the flowering season (i.e., when the greatest number of flowers were being pollinated). Hand pollination experiments showed that pollen viability and pollen deposition directly influenced seed set. These data collectively indicate that the preference of pollinators for flower color and pollen viability changed during the flowering season in a manner that optimizes successful reproduction in G. leucomelaena. This study is one of a few that have simultaneously considered the effects of both pollen viability and pollen deposition on reproductive success in the same population and on individual plants.     

Air and surface soil samples – two different pairs of shoes? Comparing the pollen spectrum on different days of the pollen season

The pollen spectra of air and surface soil samples from a rooftop (at 14 m) and from ground level (at 1.6 m) in the suburbs of Vienna (Austria) were compared. Two soil samples and two air samples were taken on four different days to account for possible differences: in winter when no pollination occurred (reference day), in spring during the main flowering of Betula (birch day), in spring/summer during the main flowering of Poaceae (grass day), and in autumn during the main flowering of Ambrosia (ragweed day). Thirty-five different pollen types were used to describe the pollen spectra. Frequencies of certain pollen types reflect a seasonal impact on both the surface soil and air samples and show a similarity between air and soil samples on most of the days. However, the seasonal impact is higher in the air samples and shows a high consistency for ground and rooftop level. Kendall’s tau correlation coefficients further substantiate the similarities of the samples especially for the pollen season days. Exceptions include the winter day when pollination was low and the air samples recorded nearly no pollen at all, and the ragweed day when Ambrosia pollen was abundant in three of four samples but not in the ground surface soil sample. Thus, (1) air and surface pollen samples record similar signals during the pollen season but not during the ragweed and winter season and (2) air and surface pollen samples show the impact of local vegetation also in pollen traps located at different heights.     

The influence of climate changes in Platanus spp. pollination in Spain and Italy

There is evidence of a significant increase in air temperature in the northern hemisphere over recent decades, with consequent changes for anemophilous pollen. In this work we present the effects of climatic change on Platanus spp. pollination in different areas of Italy and Spain, characterized by different climates. In particular, the historical series of pollen monitoring and meteorological data of two Italian stations, Perugia (1982 – 2003) and Torino (1985 – 2003), and two Spanish stations, Santiago de Compostela (1992 – 2003) and Vigo (1994 – 2003), were analysed. The changes recorded in all stations included the timing and behaviour of pollen release. However, no or minimal influence on the total pollen emission was found. Research has linked the changes in phenological events to an increase in temperature, moreover in this study temperature changes are believed to be mainly responsible for the variations recorded in the pollen season of Platanus. A previous start of pollination (?0.66; ?1.21; days/year) is reported in both Italian stations where the temperatures have significantly increased and a delay of 0.2 – 0.8 days/year in Spanish stations where a different trend of temperature is recorded. Other important data is given regarding the type of discharge of pollen grains during the pollen season. Pollination curves are examined by two statistical shape parameters (kurtosis and skewness) which show that pollen release is more gradual with higher temperatures or faster under colder conditions. A regression analysis links the atmospheric pollen presence to mean air temperature.     

Trends in pollen season characteristics of Alnus,Poaceae and Artemisia allergenic taxa in Bratislava,central Europe

Over the period 2002–2019, air temperature and precipitation significantly increased regionally for Bratislava, which could lead to phenological changes in some plant species. This study aimed to analyse the changes in the intensity, timing, and duration of pollen seasons of three allergological important plant taxa (Alnus, Poaceae, Artemisia) in the study area over 18 years. The pollen sampling was performed using a Hirst-type sampler. Mann–Kendall tau test was used to determine trends in pollen season characteristics, while Spearman’s correlation analysis was used to identify the relationships between the characteristics of pollen seasons and both air temperature and precipitation trends. The notable changes in the pollen-season-related features were observed for all analysed taxa. The Alnus pollen season now reaches the peak earlier and its intensity is rising in line with the summer-autumn temperature increasing trend, while unexpectedly intensity and duration of the Artemisia pollen season are declining in line with the increased precipitation and/or temperature trends. On the other hand, the intensity of the Poaceae pollen season is also declining, however, without statistically significant correlations with recorded increases in meteorological parameters considered. This phenomenon is probably related to both the reduction of the area of grasslands due to urbanization and the implementation of effective maintenance of urban green areas (e.g., timely mowing preventing the repeatedly flowering of grasses).

     

Pollen germination and pollen tube growth in Fraxinus pennsylvanica

With regard to adaptation of green ash (Fraxinus pennsylvanica Marshall) to ecological conditions in Croatia, pollen germination and pollen tube length after 2, 4 and 6 hours were examined in vitro at 10, 15, 20 and 25°C during two years 2001 and 2002. Narrow leaved ash (F. angustifolia Vahl) pollen served as a control in 2002. The year, time and temperature, and the interaction between time and temperature were significant for both germination percentage and pollen tube length. Interactions year × temperature and year × time were significant for pollen tube length only. The highest germination percentage (17.86% in 2001 and 19.40% in 2002) of green ash pollen was at 15°C after 6 hours. The pollen tube length was greatest at 20°C (393.46 μm) in 2001 and 25°C (899.50 μm) in 2002 after 6 hours. Narrow leaved ash pollen had the highest germination percentage (19.22%) at 20°C after 6 hours and was significantly reduced at 25°C. The pollen tube length was greatest at 25°C (518.90 μm) after 6 hours. It can be concluded that green ash pollen has satisfactory germination in ecological conditions in Croatia and that the optimum temperature for pollen germination is higher than 20°C.     

Airborne pollen concentrations,solid particle content in the air and allergy symptoms in Córdoba (Spain)

During 1991 and 1992, hourly measurements were taken of solid particulates (size, 22–25 μm).Olea and grass pollen and spores. The results were then compared with symptoms recorded in patients consulting the Allergy Unit during the period of highest pollen concentrations (April–June). The spore-trap slides were studied by spectrophotometry in order to analyse the total solid particulates content in the air as a possible synergic agent of the pollen. This allowed the volume of material present in the air to be determined and expressed as a percentage of total optical density (OD). Allergy symptom data were obtained from the study of subjective clinical records completed by patients, who were required to note down the severity of a selected series of symptoms every 4 h using a scale from 0–3. The results showed a clear link during the season between hourly peaks and pollen concentrations, and the different patterns of response associated with the dominant pollen types. An attempt has been made to determine whether a relationship exists between the increment of the optical density and the symptomatic response. The positive relationship encountered seems to indicate that a synergic agent takes an active part in the effects produced by pollen in the patients.     

Airborne pollen grains in Nsukka,Nigeria

A study of the airborne pollen grains in Nsukka, Nigeria, has been carried out at two different sampling heights (1.8?m and 15?m) from February 1993 to January 1994. Twenty‐six plant families (40 genera) were identified at the lower sampling height, whilst thirty‐eight families (58 genera) were identified at the height of 15?m. A total of nine and eighteen fern spore types were observed at 1.80?m and 15?m, respectively. The quantitative results indicate that the number of pollen observed at 15?m sampling height was statistically different (p<0.05) from that observed at the height of 1.80?m. The analysis of airborne pollen grains indicates three different periods: (1) dry season, (2) rainy season, and (3) late rainy season to early dry season/Harmattan. The highest pollen abundance was recorded during the late rainy season – early dry season/Harmattan followed by that of the dry season. The predominant pollen grains and fern spores trapped at both heights include Poaceae, Casuarina equisetifolia, Milicia excelsa, Elaeis guineensis, Celtis integrifolia, Alchornea cordifolia, Amaranthaceae/Chenopodiaceae, Combretaceae/Melastomataceae, Nephrolepis biserrata, Thelypteris totta, and Dryopteris spp.     

Airborne pollen and spores of León (Spain)

A qualitative and quantitative analysis of airborne pollen and spores was carried out over 2 years (from September 1987 to August 1989) in the city of León. Slides were prepared daily using a volumetric pollen trap, which was placed on the Faculty of Veterinary Science building (University of León) 12m above ground-level. Fifty-one pollen types were observed; the most important of these were: Cupressaceae during the winter,Pinus andQuercus in spring, and Poaceae, Leguminosae and Chenopodiaceae in the summer. The results also showed the existence of a rich mould spore assemblage in the atmosphere. The group of Amerospores (Penicillium, Aspergillus andCladosporium) as well as Dictyospores (Alternaria) were the most abundant;Puccinia was common in the air in August. Fluctuations in the total pollen and spores m³ of air were compared with meteorological parameters (temperature, relative humidity and rainfall). From the daily sampling of the atmosphere of León, considering the maximum and minimum temperature and duration of rainfall, the start of the pollen grain season was observed generally to coincide with a rise in temperature in the absence of rain.     

Predicting the grass pollen count from meteorological data with regard to estimating the severity of hayfever symptoms in Melbourne (Australia)

In Melbourne, Australia, grass pollen is the predominant cause of hayfever in late spring and summer. The grass pollen season has been monitored in Melbourne, using a Burkard spore trap, for 13 years (1975–1981, 1985 and 1991–1997). Total counts for grass pollen were highly variable from one season to the next (approximately 1000 to >8000 grains/m³). The daily grass pollen counts also showed a high variability (0 to approximately 400 grains/m³). In this study, the grass pollen counts of the 13 years (12 grass pollen seasons, extending from October to January) have been compared with meteorological data in order to identify the conditions that can determine the daily amounts of grass pollen in the air. It was found that the seasonal total of grass pollen was directly correlated with the rainfall sum of the preceding 12 months (1 September–31 August): seasonal total of grass pollen (counts/m³)=18.161 × rainfall sum of the preceding 12 months (mm) −8541.5 (r _s=0.74,P<0.005,n=12). The daily amounts of grass pollen in the air were positively correlated with the corresponding daily average ambient temperatures (P<0.001). The daily amount of grass pollen which was to be expected with a certain daily average temperature was linked to the seasonal total of grass pollen: in years with high total grass pollen counts, a lower daily average temperature was required for a high daily pollen count than in years with low total grass pollen counts. As the concentration of airborne grass pollen determines the severity of hayfever in sensitive patients, an estimation of daily grass pollen counts can provide an indication of potential pollinosis symptoms. We compared daily grass pollen counts with the reported symptomatic responses of hayfever sufferers in November 1985 and found that hayfever symptoms were significantly correlated to the grass pollen counts (P<0.001 for nasal,P<0.005 for eye symptoms). Thus, a combination of meteorological information (i.e. rainfall and temperature) allows for an estimation of the potential daily pollinosis symptoms during the grass pollen season. Here we propose a symptom estimation chart, allowing a quick prediction of eye and nasal symptoms that are likely to occur as a result of variations in meteorological conditions, thus enabling both physicians and patients to take appropriate avoidance measures or therapy.