The trick is to stay dry. Pick up a bunch of GOOD QUALITY ponchos, not the cheap $1 ones (or the $$ ones they sell at the stadium that smell like a landfill). Target and Walmart sell great ~$5 ponchos made out of thick plastic.

They also sell re-fillable hot cocoa mugs at the stadium. Nothing warms the body on a cold football night better than some hot cocoa.

Snuggle up! When you are in a stadium with your 50k closest friends it never gets super cold. Just sit next to other fans to shield each other from the wind/cold.

If you need to get warm or out of the rain/snow you can always walk around the stadium. Visit the stadium store... Find a snack.. etc.