A couple of weeks ago, the temperature in New York dropped something like 30 degrees in the span of a day. A month or so earlier, the city had seen the reverse— a 40-something-degree day was followed soon after by an unseasonable 70-degree one. Weather is my favorite boring thing to talk about, so whenever I saw someone after these rapid temperature changes I said something like, “Crazy weather, huh?” Usually they replied “Yep!” or “I know,” bringing our conversation to a welcome early close. But a few friends I spoke to instead took this opportunity to introduce my second-favorite boring discussion topic: mild seasonal illness. “I’m sick,” they’d say. “It’s because of the weather.” Always, I’d nod. This is a line of thinking I have heretofore taken as self-evident truth—a sizable change in temperature, in either direction, can give you a cold, or a cough, or a sore throat. The reason is ... well, I didn’t know the reason, actually. (Something about barometric pressure, maybe?) Many places experience a number of wacky weather reversals at every changing season, but not everyone falls sick every time. So who is susceptible, and why?
As Ray Casciari, a pulmonologist at St. Joseph Hospital in Orange, California, told me, changing weather can make you sick, but it has less to do with the actual temperature change, and more to do with environmental effects associated with those changes. Research shows that, despite what your mom has told you, simply existing in cold weather isn’t, itself, likely to make you get sick. A 2002 meta-analysis examined related studies, and concluded that exposing one’s skin to cold temperatures does not put one automatically at risk for contracting the common cold. As such, there is no direct link between avoiding the cold and staying healthy. As Casciari puts it, “Staying indoors, bundling up, and not exercising is supposed to make you get better faster. Not so.”