Ever noticed that when you’re freezing, your neck’s still warm?
Ever noticed that when you’re hot, your neck typically sweats enough that it’s cool?
Why?
Isn’t there a major artery that goes straight from your heart up through your neck? I would guess that you’re getting much quicker blood circulation through your neck than anywhere else, so it would stay warmer. When the air temperature is cold, your extremities tend to be much cooler than the center of your body.
I sweat all over, not just my neck. I think most people sweat the most from their underarms. Your neck would tend to get cooler because it’s exposed to the air. Your underarms generally aren’t, so the sweat can’t evaporate. If you stood outside naked, your body would probably cool all over at a similar rate (but don’t try it 
). Evaporation is what causes the cooling effect from sweat.