When the temperatures start to drop, Wood Frogs will go bury itself and then shuts itself down. As the temperatures get harsher, the frogs create glucose in their liver by breaking down glycogen using enzymes. This glucose goes out into their body organs and is distributed throughout the bloodstream.
The Wood Frogs are one of serveral species that have the amazing ability to completely freeze solid! (Peepers can do the same...except that in their case they have lots of glycerol, not glucose, in their system)
Since there's so much glucose in the Wood Frog's system, their organs don't get damaged because the sugar in their blood acts as anti-freeze. They can stay completely frozen like that for 2 weeks or more. They stay frozen for as long as the temperature of the ground is below freezing. They have no choice. They are the exact temperature of the environment they are in. When they thaw out, it's like an icecube coming to life!

(http://allaboutfrogs.org/weird/strange/freeze.html)