Hibernation in ectotherm and endotherm
Weasels don't hibernate.  See http://icwdm.org/handbook/carnivor/Weasels.asp

Both will die when the temperature falls below a certain level.  The difference between snakes (ectotherms) and weasels (endotherms) is that the snake's body temperature will fluctuate more, depending on the surrounding temperature.