It is probably more a problem of lubrication than freezing water....

This happens a couple of times each winter.  When we have a heavy rain
that turns to snow followed by a hard freeze, The driver side door has
problems.  First the latch is hard to operate and then the door won't
stay closed.  After running the heater for fifteen minutes the door will
stay closed.  Where would the water be getting in?  I would like to
cover the area during the rain to prevent this problem.

                 ---MIKE---