The cold can be hard on your house and garage keys too. Locks become very stiff when they are cold, and if you're not careful you can end up twisting, cracking or even breaking your keys off in the lock. This key had been weakened by years of winters, and has been slightly twisted and cracked for years. When we got home the other night and I locked the garage, the key just kept turning. My first thought was, "Uh oh..." Sure enough, this was all I had left in my hands.
Fortunately there was enough left sticking out of the lock that I could remove it easily with pliers - though when say "easily" I really mean "with more effort than you would expect" because the tumblers and pins in the lock were also stiff reluctant to move in the cold.
Fortunately I have a spare set of keys. Getting some new copies made has been on my do to list for quite some time. I think I might actually have enough time to sneak away from work today to get them cut... unless I get another project or surprise meeting dropped on me at the last second again.