I don't have any issue with my sims changing into cold weather clothes when they go outside. But they never change into everyday clothes when they come back inside so I have to use the change outfit option to get them back into indoor appropriate clothing.
But in my homes with basements, they always change into cold weather clothing when they go into the basement in winter.
This problem started with the latest patch - May, 2021. Before that, they would change into cold weather clothes when going out but not in. They would also be in cold weather outfits after going into CAS or changing worlds. I do have all packs and kits. I also have mods and CC but haven't added anything new since the patch. They definitely feel the cold - one of the children froze to death when coming home from school. She stood outside the house and because it's a large family I didn't notice her until I saw the urn. Luckily, I had saved prior to that so I could quit and go back. I noticed also that they do not change into cold weather clothes when going to and from work. I play 5 families rotationally and it happens to all. Also, NPC's are walking around without cold weather clothes. This occurs all the time in winter regardless of temperature even during a blizzard.
EDIT - I took out all mods and all CC and it still does it. I cleared all caches, too. I made a new family and had them move to different worlds and it did it in every world.
I have this too. One of the most frequent reasons why a sim dies in my game is if you go to the gym during winter or organise a party during very cold weather.
In the gym, even when most of the sound com inside there is always a group that stays outside talking, doing sit-ups, or just stand there. They stay outside in their gym clothes instead of changing to winter clothes, until they freeze to death.
If you organise an even in winter, most of the time Sims arrive in their party clothes (which makes sense I guess, because it's a party) and many times they stay outside, talking, instead of coming inside, until they freeze to death. It is so annoying that I ended up turning weather effects on Sims OFF. So 2 problems here: One, they do not change clothes to winter clothes when outside. and two, the AI seem unable to take action changing clothes or seeking warm temperature inside, and instead they simply freeze to death.
