I spray a little WD40 in my locks when the weather man say it's going to be freezing and it will keep all locks from freezing. But if you do have a frozen lock, spray the WD40 in your keyhole and it will unthaw it quickly. Use around doors and anything that will freeze. It really works.
This page contains the following solutions.
If you are having cold weather and one of your locks outside has stopped working, the chances are it has frozen. Try heating the lock with a hair dryer until you are able to turn the key.
