What is "wind chill" all about?

It’s not just that your brain thinks it’s colder than it really is; because of the wind your skin is losing heat faster, and frostbite will occur more quickly than if there is no wind. Trust me on this - i’m from Saskatchewan, and our sadistic announcers on the CBC begin their weather casts on windy days in January with cheery little bulletins like: “Exposed flesh will freeze in 30 seconds.”

Here in Virginia, the yearly concern is the opposite effect: heat index. You have to sweat more in our humid environment to get an equivalent cooling effect.

Conversely, in the winter the humidity compounds the wind chill.

What I want to know is at what temperature and/or wind speed does the humidity affect neither wind chill nor heat index.

I too grew up with those cheery little CBC weather reports. “Temperature is -25, but with the wind chill -58…” I always sort of disbelieved them, because I’d walk to school against the wind (a 25 minute walk) with my face exposed, and it wouldn’t freeze. I always figured that either I was weird (but all my friends did it too) or the weather people exaggerated.

Not so. All else being equal, the wind chill on a dry day will be more severe (ie, colder) than the wind chill on a humid day.