Noticing the sniffles all around you? It's a fact of life that colds are more prevalent during the winter months, even in areas spared freezing temperatures, such as Hawai'i. Here, colds usually come during the rainy season.

In an effort to find out why flu season comes along at this time of year, researchers found that the flu virus is more stable and stays in the air longer when the air is cold and dry. The flu may start its spread in colder regions, then pass along throughout the globe.

Furthermore, with people spending more time inside when it's cold or rainy outside — especially children in school— there is more exposure to viruses that cause colds, and illness is spread more quickly.

"They are more common this time of year, plus you are more likely to be exposed to other people because of an enclosed environment," says Dr. Jim King, president of the American Academy of Family Physicians.

"All colds, flus, whatnot are caused by an infection, either a virus or bacteria," says King, a family physician in Selmer, Tenn. "It has nothing to do with temperature in the room, whether it be hot or cold. It's an exposure to an organism you're not resistant to."

Children get, on average, three to eight colds a year, according to MedlinePlus, a health information Web site from the federal government.