Do you get itchy eyes and a runny nose the same time every year? If so, you're not alone. Seasonal allergies, also known as hay fever, affect as many as 1 in 5 Americans.

But the culprit isn't hay. It's pollen.

You can find it in the air from early spring to late fall-and all year round in warmer climates.

Generally, tree pollen is most common in spring, grass pollen in summer and weed pollen in fall.

It can reach us from far away. Samples of ragweed pollen have been collected 400 miles out at sea and two miles high in the air.

So how can you get away from it? Watch the weather forecast.

That's right: In addition to sun, rain and wind, meteorologists can predict pollen levels.

They count how much pollen is floating in a cubic foot of air. But they don't hold a magnifying glass up to the sky.

Instead, they attach a rotating rod covered with a sticky substance to the roof. After 24 hours they measure the amount of pollen attached to the rod; this gives them a good estimate of how much pollen is in the air.

Counts tend to be highest early in the morning on warm, dry, breezy days and lowest during colder, wet periods.

Pollen counts aren't exact, but they 're a good way to tell when it's best to stay indoors.

If you go outside anyway on a high-pollen day and find yourself sneezing like crazy, I promise not to say I told you so.