I'm up in the northeast, had they locks freeze a couple of times. The best thing I've found for the locks is from Toyota. They sell a can of Toyota silcone spray that you can use to lube the tailgate hindges, locks, engine hoses, etc. Its a red and black can if I remember correctly. You put the little tube on the can, stick the tube directly into the keyhole and spray, then spray the locking mechinism and door hindge. It repels moisture, and havent had a stuck lock since then. Theres probably others who make the silicone spray, but the Totyota one has worked well. It lasts a long time. Think the can was $4.99.