Lori
while the OP did ask specifically about frost bite; I agree with you that most hypothermia cases happen at more like 35 to 45 degrees with people wearing much too little, and most often in Spring or Fall when runoff can trap people.

Longhair and I were hiking out of the Cascades in a slight snow when we were overtaken by a lone runner wearing nothing but shorts, shoes and a tee shirt. It was 25 miles around the mountain and he said he would be warm enough if he kept running so he couldn't stop to talk to us. The locals here (In Bend) think nothing of this and often carry no water on hikes and carry nothing at all, but wearing a cotton hoody.

Jim