These counts are of interest to some 35 million Americans who get hay fever because they are allergic to pollen.
People also look for counts of mold or fungus spores.
These are another major cause of seasonal allergic reactions. Pollen and mold counts are important in helping many people with allergies plan their day. Pollen is a very fine powder released by trees, weeds and grasses. It is carried to another plant of the same kind, to fertilize the forerunner of new seeds. This is called pollination.