Why is flu season in winter?

We all know that winter is flu season - but why? That turns out to be an interesting question and some of the answers you may have heard have been shown to be incorrect.

Check out this illustrated guide from Popular Science.

Here's the bottom line but it's worth checking out the link:

Quite possibly, the flu's annual winter-time parade through our immune systems has to do with both factors: the virus survives better and transmits more easily in cooler, drier air. The case isn't closed yet--and researchers are still looking into some of those other theories, like the idea that our immune systems are weaker in winter--but, for anyone looking for ways to avoid the seasonal flu (in addition to the flu shot, of course), a portable humidifier seems like a good place to start.