Do hibernating bears ever leave their den during winter if the weather gets unusually warm? hibernating bears are prompted to come out of their den both by warming temperatures and by increasing day length [normally late March to early April]. thus, a January thaw typically will not fool a bear into coming out early. However, some bears may find themselves in a wet den when temperatures get warm, with snow melting around their den, and this could force them out.
Bears also may be more prone to disturbance from humans during warm spells when they are not hibernating as soundly, and this could cause them to vacate their den. After abandoning their den, they will typically find another suitable site that they already know about. However, any new den would not have the bedding material that bears rake in during the fall when they are preparing for hibernation. Dave Garshelis, DNR bear research biologist.