Grass pollen season begins in early March and doesn’t end until grasses stop releasing pollen in mid-October. As grass releases pollen into the air, the wind can carry it for miles on dry, sunny days. Pollen counts are usually lower on damp or cool days. Grass pollen is microscopic. Though you may not see it in the air, if you’re allergic to grass pollen, you may experience a reaction even to small amounts of it.