When I'm dressing my Sims, I like to give them two outfits for sleep, athletic, and cold weather. One outfit that would work well with cooler weather and the other for warmer weather.

For sleepwear outfits, one is a shorts and t-shirt/tank top combo and the other is long sleeve shirt, pajama pants and slippers. If I feel a sim would wear a night gown instead, I will do a short one and a long one. Some Sims I do a combo of both (nightgown for warm weather, pants for cold weather).

For Athletic outfits, one is usually one of the spa day outfits and the other is shorts and a short sleeve shirt or one of the athletic dresses depending on the Sim.

For the cold weather outfits, I like to have one that's just a sweater/sweatshirt and pants, while the other is a jacket with a hat and gloves. For Sims who would more likely wear a dress or skirt rather than pants, I usually have them wear leggings and socks under their dress/skirt.

Sometimes I do a combination of Skirt/pants for warm and cold weather too, depending on the Sim.

My sims are usually pretty good at wearing the right outfit for the weather in this way.