A pollen count gives the number of grains of pollen in a certain amount of air in a set time period (usually 24 hours). The pollen is measured for specific plants such as grasses, oak trees and cottonwood trees.
Pollen counts change with the weather (rain, humidity, sun and wind) and time of day. For example, they’re usually higher on warm, breezy days and lower on chilly, wet days. Some places give a total pollen count rather than pollen counts of specific plants. A high total pollen count doesn’t mean you will have allergy symptoms. The pollen from the plant you are allergic to may not be high.