BACKGROUND: The observation of low levels of weed pollens following a freeze and an early autumn snowfall in Denver, Colorado led to this analysis of meteorologic variables and pollen counts. OBJECTIVE: The purpose of this study was to examine, in depth, the relationship between observed pollen counts and a selection of independent meteorologic variables. METHODS: We prospectively studied in 1991 daily high and low temperature, relative humidity, precipitation, barometric pressure, percent sunshine, wind velocity and direction, tree, grass, and weed pollen, as well as dates of the first frost/freeze. Similar data were retrospectively analyzed for 1987-1990. RESULTS: Correlation coefficients for the prospective data were as high as .611 for high temperature and cottonwood and .718 for high temperature and maple (P < .001). High and low temperature showed strong correlations with the combined weed counts (.598 and .628, respectively, P < .001). CONCLUSIONS: Denver weed pollens appear impacted more by temperature and less by precipitation and humidity, while the converse is true for tree and grass pollen. However, weed pollen, especially sage, may appreciably rebound after freezing temperatures. While separate meteorologic variables may have high correlations with specific pollen counts in a given year, such effect is not consistent and varies from year to year.
BACKGROUND: The observation of low levels of weed pollens following a freeze and an early autumn snowfall in Denver, Colorado led to this analysis of meteorologic variables and pollen counts. OBJECTIVE: The purpose of this study was to examine, in depth, the relationship between observed pollen counts and a selection of independent meteorologic variables. METHODS: We prospectively studied in 1991 daily high and low temperature, relative humidity, precipitation, barometric pressure, percent sunshine, wind velocity and direction, tree, grass, and weed pollen, as well as dates of the first frost/freeze. Similar data were retrospectively analyzed for 1987-1990. RESULTS: Correlation coefficients for the prospective data were as high as .611 for high temperature and cottonwood and .718 for high temperature and maple (P < .001). High and low temperature showed strong correlations with the combined weed counts (.598 and .628, respectively, P < .001). CONCLUSIONS: Denver weed pollens appear impacted more by temperature and less by precipitation and humidity, while the converse is true for tree and grass pollen. However, weed pollen, especially sage, may appreciably rebound after freezing temperatures. While separate meteorologic variables may have high correlations with specific pollen counts in a given year, such effect is not consistent and varies from year to year.