I am going to take a wild stab and then get blasted by a bunch of BF doctors, etc. I would think that being out in 40F weather for over 1:45 (and moving) would cause your body to protect your tempurature by "pulling" the blood from the skin (constricting the capillaries), where it is getting cooled, to the core to keep the vitals warm. It probably takes a few minutes for the capillaries to reopen, so the skin would still be cooler than body tempurature.

But that is just a guess.