My brother the science trivia whiz says that you can "flash freeze" your lungs by breathing air at -40F. I have not confirmed this with a reliable web site or other source. 15 miles in -25F would be tough. What, that is about 1.5 hours? I've been out in 10F weather for about 1.5 hours and my toes were frozen solid and painful to thaw for hours. I imagine there is proper clothing to survive those temps, but probably beyond the typical winter commute. Nope, definitely not whimp territory. Hats off for even considering it.