According to the American Academy of Allergy Asthma and Immunology, pollen levels vary from location to location and day to day for several reasons. Weather can influence pollen counts, which then affect hay-fever symptoms. Allergies are less likely to flare up on rainy, humid, cloudy, or windless days because pollen does not move about in these conditions. In addition, rain can wash pollen out of the air, and some plants don't pollinate in damp weather. On the other hand, allergy symptoms are likely to worsen during hot, dry, and windy weather. Urban areas tend to have less pollen-producing vegetation, and areas near large bodies of water tend to be relatively pollen-free.

Grass-pollen season stretches from March to October, peaking in most states during the summer months. To see how your town compares with other cities when it comes to pollen counts, check out the American Academy of Allergy Asthma and Immunology (www.aaaai.org), or visit Pollen.com (www.pollen.com) to get a local pollen forecast for anywhere in the country. You can also sign up for free allergy alerts via E-mail so you know first thing in the morning if pollen levels will be high that day in your town.

—M.H.