In my experience there are two things that cause car doors to freeze shut in extreme cold: one is rain (or wet, melting snow) followed by extreme cold and wind. The other is washing your car, and parking it soon afterward and then a big temperature drop.

The 'carwash freeze' is the worst, and all doors and windows and trunk could be compromised. You might have to pick a door and pry it open with a wooden shim. This can be avoided by driving the car for 20 miles or so with the heater on before parking.

The rain/freeze can be mitigated somewhat by parking the car in the sun so only one side faces the prevailing wind. The other side will not freeze.

Returning to a thread I started last winter...

As it turned out, I was away on business during the big freeze these past several days. Anticipating snow, I silicone lubed the rubber trim on the doors. At the airport, I parked the car at the (uncovered) economy lot, and I hide a can of deicer under the car. As it turned out, the snow wasn't terrible at my airport. However, there was enough ice on the windshield that it took a bit of time.

What I didn't expect was that the water dripped down from my car and froze on the can of deicer, completely encasing the spout and button. Fortunately, a few whacks with a knife took care of it. I almost looked really stupid: a deicer rendered useless by ice!

I had a similar problem just the other day. The padlock was OK but the hinges were encased in ice. I needed a shovel to break things up. Pretty minor compared to parts of the county where it looks like entire states are encased in ice.

the canoe racks that stay on my old Kanoe Kar year round don't fit %100,they are from another car long gone.so in summer i get a bit of water past the extra gasket i put on the door.
in the winter it's WD40 and a crowbar......

I never thought I "needed" remote start, but the "return to the airport" after bad weather scenario is where this really shines.

I can start the Jeep from the plane once we land or from baggage claim. The key fob has pretty good range, but The UConnect app on my phone can connect to the Jeep from anywhere I have internet. By the time I get to it, the windows are cleared, it's warm enough to probably soften the ice around the doors, (at least so far I've never had stuck doors.) Toasty warm heated seats and steering wheel. Man I'm getting soft. Now if it could drive me home while I nap...

Self driving cars are on the horizon. California is reputedly preparing the regulations which will allow field testing in just a few years.

What do you do with this combination? Most people seem to use wood shims to avoid damaging the door.

Do I need to pack a little prying bar?

You don't pack a pry bar?

If the door is frozen, don´t pry, but push the door in a little bit (should be a little play in there), repeat as needed. This will brake/weaken the ice and will loosen the door.

Keep the locks lubricated and just in case if it freezes. A little bottle of lock anti-freeze is always handy to fix a frozen lock(unless you stored the bottle in the car).

Returning to my car from the theater with my wife one winter night, I was annoyed to find my (driver's side) door lock frozen over.
Cursed, tugged, even torched it a bit with a bic. No joy. Just when I was ready to look over the top of my car to my wife, the door opened.... "what are you doing out there, she said".

Seems as if HER door was fine. She got in, sat down, and waited to see why I was dancing about in the cold. When she got bored, she pushed open my door from the inside. No problem. Much humiliation, though.