You wake up on a frigid winter morning and check the weather on your phone. It says it's 38ºF outside with a wind chill of 31ºF. So, freezing. But when you look out the window, you can clearly see puddles of liquid water. Not freezing. What's up with that? This is what: wind chill doesn't tell you whether it's freezing outside; it just predicts how fast you'll get frostbite. And, as it turns out, it's even pretty lousy at that.