A lot of people notice their skin behaves differently across the year: worse in the dry cold of winter, or in the sticky heat of summer, better on a calm mild day. Weather is one of the most common things people suspect, and also one of the hardest to prove, because you can't change it to test it. A simple diary is the honest way to find out whether it really matters for your skin.
Cold air holds less moisture, indoor heating dries the air further, heat brings sweat, and pollen rises and falls with the seasons. Any of these can affect skin, but they also change slowly and all at once, so it's easy to assume "it's the weather" without ever checking. The only way to know is to write down the weather next to how your skin felt, day after day.
You don't need a weather station. A few words is plenty:
One bad skin day on a cold morning proves nothing. A pattern that shows up again and again across several weeks is what tells you something real. Weather effects are gradual, so the useful comparison is often week to week, or the start of a season versus the middle of it.
Some people flare in dry cold, others in humid heat, and plenty notice no clear weather link at all. There's no universal rule to copy. The point of tracking is to find your pattern, not someone else's, so you can plan around the times of year that tend to be harder for you.
This is general, practical information, not a diagnosis or treatment recommendation. If you're concerned about a skin condition, it's always worth talking to a doctor or dermatologist alongside anything you track yourself.
This is exactly what I built SkinFam for, a private, on-device diary for eczema and skin flare-ups. It even notes the day's weather for your area next to your entries, so the connection is easier to spot over time, and nothing you log ever leaves your phone. Search "SkinFam" on the App Store.