I have a 91 Sierra truck. Earlier today it rained, then got cold and
later I could not get into the truck.  I finally managed to open one
door on pass side.  The driver door is still stuck.  I was not within
close reach to an outlet to use a hair dryer.  At least now I moved
the truck near an outlet.  If I had not been able to pound with my
fist and force the door I would have been locked out.  Using a torch
on the paint did not seem like a good idea.  But without electricity
there would have not been another way.

My thought is that what is needed is a preventative measure.  Applying
something around the door seal.  But what?  I'd rather not use
something that will get all over my clothing, like auto grease.  I
suppose vaseline would not be too bad of a mess, but maybe there's
something else.  Does anyone have any ideas?  My other thought is
silicone spray, but that seems to evaporate in a short time.

What can I use?  

I should mention that I have had this problem on other vehicles, but
because of the door design, this truck seems to get worse.

Thanks for all advice

Bob