In most of North America, bats hibernate from late fall until early spring. They often seek out caves and abandoned mines, and will migrate from their current homes (buildings, bat houses, etc.) to warmer, more secure places. Some species, such as the Mexican Free-Tailed Bat, migrate in the winter to warmer climates such as Mexico.
Some bats in warmer climates do not hibernate. Instead, they go into a state of torpor, or temporary hibernation, if outside temperatures approach 32°F. Torpor is a state of inactivity in which the bats stay in their day roosts for extended periods of time to conserve energy until temperatures begin to rise.