A pollen count is a measurement of the number of pollen grains in a given volume of air. Pollen counts, and forecasts of pollen conditions, are routinely produced and reported to the public because high aerial pollen concentration is associated with increased rates of allergic reaction for those with conditions such as hay fever and asthma. The pollen counted are usually identified to family; particularly families with hyperallergenic pollen (e.g. grasses, family Poaceae) and families that are prevalent in the relevant area. Thunderstorm asthma events as well as mild winters with warmer days lead to increases in pollen counts, while colder winters lead to delayed pollen release. Though not pollen, hyperallergenic fungal spores such as those of Alternaria may be counted as well.