When do newts come out of hibernation?

Many amphibians hibernate because they are unable to regulate their body temperature like mammals and birds. They allow their body temperature to drop to extremely low levels and their bodily functions slow way down. In this way they don't need to run around searching for food because they don't need to burn energy to keep warm or maintain other bodily functions. When the weather warms up again, their body returns to normal and they function at optimal body temperatures again.

Keep in mind this is only the case for some amphibians. In warmer or tropical climates it may not be necessary because it may never get cold enough to warrant hibernation.