The type of vegetation in your own area, whether native trees, ornamental or agricultural, contributes to your exposure. Pollen also possesses diurnal variation . This means pollen grains are generally shed in the early morning hours. Later in the day, weather conditions and wind speed affect how much pollen becomes airborne. Because mold is more greatly affected by day to day weather conditions, its overall prevalence in the air is harder to predict than pollen.
Molds occur all year, with peaks in spring and fall .
They are closely tied to temperature and humidity. The mold count is very low during cold wather, especially when snow is on the ground. Mold count is highest during late summer and early fall, due to decaying vegetation. Parasitic fungi such a smuts and rusts are numerous during harvest time, as their spores become airborne. Several types of fungi comprise the daily mold count.