They actually don't hibernate, they eat the honey during the winter, and flutter their wings to raise their body temp, and circulate air inside of the hive for warmth. They're kinda self contained until the ambient temp warms up.
At least that's what my wife, the bee keeper, tells me.....
Wife tells me the hives need insulation when the temps get close to freezing overnight. Natural hives are better insulated that the wooden man made hives. As my wife has told me bees survived cold winters for centuries without help from us.