Check your car keys for winter and ...

[Bill Dufour]

I got a spare key made for my wifes car and put it away. I remembered after a month and it had issues. The original did too. Turns out the door lock needed cleaning but not the ignition lock. We never use the door key since it uses a key fob to get in.
Lesson is to check the physical key once. year to make sure the door lock is not gummed up.
With the start of the rainy seaason coming I also cleaned the sunroof drain hoses.
Bill D.

[Brian Deakin]

This tip may be useful
I was told by a locksmith to lubricate locks with graphite powder

The trunk lock our car would not open a spray of the powder ressolved the problem

[Lee Schierer]

If you live in an area prone to freezing, it is a good idea to spray your car door seals with silicone so you can open the door after parking outside.

[Alex Zeller]

Back in 2013 I got the wife a Rav4 with the push button ignition. I thought it was gimmick but after having it I would never go back to a key. Touch the door handle and it unlocks, push the start button and it fires up. The only time to actually touch the remote is if I want the rear hatch to open before I get to the car or to use the remote starter.

Along with the sunroof check your air conditioner drain hose. If it gets plugged up water will leak into the car.

[Greg Funk]

My wife's van is like this but I always forget to lock the door. I have an older car with a key fob and never forgot to lock it as I would always have the key in my hand when leaving the vehicle. With the van the key is in my pocket and I don't think about it. My other car is connected to the phone so when I walk away out of range it locks. Guess I'm getting old...

[Aaron Rosenthal]

We get a lot of rain. A little less than Seattle but not much less.
Then, in the winter, it can get below 0 Celsius (32 F) and my wife’s odyssey won’t open up.
There’s only one key slot, driver’s side door. When everything freezes she can’t get in. I’ve tried everything, but now, I use a heat gun on the lowest setting for a few second and that works.

[Andrew More]

Along with the sunroof check your air conditioner drain hose. If it gets plugged up water will leak into the car.

Second this. Had to fix my wife's AC on her 2003 Civic. Otherwise the passenger would sometimes get a surprise foot washing. The good news is that a few puffs of air from an air hose will usually unblock this, so the only real challenge is finding the hose the first time.