How do you get rid of windshield fog?

Here in Arkansas its really, really humid. So a lot of mornings I’m getting in the car to go work out and my windshield is all fogged up.

I don’t think anyone has ever really told me how to fix this, so I have to sit in my car for five minutes, fidgiting with the air to fix everything. (Usually I’ll just go driving with the windows down and sunroof open to fix this problem. Its nice when its warm out, but come on.)

Do you have a fool proof way to get rid of this fog? Is it true that you’ve got to make the air the same temperature as the air outside?

(And yes, I realize that this is a ridiculous question I shouldn’t have to ask. But how else will I learn? ;) )