If you're old enough, you can remember the time when basketball coaches admonished their players to put on their knit caps after taking post-practice showers, and punished anyone who neglected to follow that ritual by making them run laps. But that belief is about as antiquated as black canvas high-top sneakers and socks pulled up to your kneecaps.
As Dr. Donald Denmark, chief medical officer for Tuscon's Carondelet Health Network explained to TV station KVOA in 2013, the notion that you can catch the flu from going out in cold weather, with wet hair or without a coat, or by sitting by a drafty window, is contrary to what we know about how the flu is transmitted. "It's an airborne and droplet transmission, so it's in the presence of someone who sneezes or coughs," Dr. Denmark said. "You inhale the virus that is shed during that contagious period of time."
One reason that people may get mixed up about this is that the peak months for flu infections are in the winter, when it's often cold and wet outside. But medical experts think the reason for increase in illness is that people spend more time indoors, where it's more likely that they'll be exposed to microbes spewed at them from another person's sneezing or coughing [source: Brownstein].