Tempest front door problem

I own a 1989 pontiac tempest, when the weather got cold (-40) c. The front doors both stop opening I have tried everything from lock deicer to using a screwdriver to pry the doors open. Help please:confused:

are the actual key openings getting stuck or will the doors themselves not open? if its the actual doors the seals around the door might be sticking "try using some "lubricant silicone" around the seal,"should do the trick,