A few years ago I was looking for an athletic hat that I could wear in cold weather while I ran outside during Minnesota winters. Many hats I tried were too thick to be useful. The problem with thick hats in cold weather is that they can cause you to sweat a lot more than usual and a wet head in cold temperatures can be dangerous. I wanted a cheap alternative that would keep my head warm, yet breaths enough to be comfortable on a winter run.

The sleeves of common cotton t-shirts typically fit snugly over the head (provided your head and arms are proportionate to each other). The cotton material can keep your ears and head warm, but still breath enough so that your head does not overheat. Any old t-shirt that still has a little life in the sleeves will do. Just cut off the sleeve at the seam, sew up the end you just cut away with a sewing machine or needle and thread, and turn the sleeve inside out to hide the seam you created. Your hat is done, and it didn't cost a dime.