Well to answer that question let’s look at the conventional wisdom. If you ask just about anybody off the street, they’ll tell you that the cold somehow weakens your body (maybe your immune system) and makes you more susceptible to disease. How do they know this? Well their mothers told them, of course!
From the Upcoming ueue, submitted by Geeksaresexy.
I work in an office of only four people, and I stay active outdoors through the winter. I'm not exactly in top physical shape, I'm just an avid yet casual (non-competitive) skier.
I always assumed that I avoided colds and flus because I'm not in a closed space with a lot of people, and because I try to make sure I'm getting a good balanced diet with vegetables in the winter instead of the heavier, high protein and carb diets that some people tend to have in the winter.
But that's not scientific, it's just personal observation. Could be just lucky. My wife has already had the really bad cold going around here, but it passed me by.
But now that I've said that, I'll expect to get sick this week!
I put scientific in quotes because that explanation does not sound very scientific to me at all, more like something my grandmother would come up with.
For a great many people, the average day looks like this: get up, go to work, go back home, etc. This routine does not really change with the seasons. So we don't really spend that much more time outdoors in the summer than in the winter.
Also: what about people who work in the outdoors all the time, like construction workers, farmers, they never get the flu?