@XXITALIANPEACHESXX
You're failing to understand how this system works. The game doesn't care how covered a sim is. Right now the only way to protect a sim in freezing weather is for them to actually be in their cold weather outfit (and same for heat waves). See below. The girl is in her cold weather outfit. I set a bathing suit as the outfit but the game doesn't care. The guy is in a everyday outfit with long sleeves and pants and is currently about to die.
https://photos.smugmug.com/photos/i-wxRTSTG/0/7750c475/XL/i-wxRTSTG-XL.png