2001 BMW X5 door locks freezing

this is a door lock problem... whenever the vehicle is parked outside in frozen conditions all of the doors and door locks freeze shut. the locks, the door jams, everything. this happens every time it is exposed to snow or ice and is parked outside. eventually when it thaws enough everything works fine, but sometimes it takes hours... is there anything i can treat the doors with to keep this from happening?

thanks very much....

mark smith