If someone is cold and you have extra layers to spare, offer to loan them your jacket/sweater/cardigan/ ect.
For example, you went to the movie theater with a group of friends. Your friend forgot that the inside of a movie theater is usually chilly so they only wore a tanktop, meanwhile you’re wearing a cardigan or jacket AND have long sleeves, ask them if they want to borrow your cardigan or jacket for the duration of the movie.
If you have extra layers to spare, and someone else is cold because they forgot to bring enough layers or wear something with sleeves, or maybe you just have a higher cold tolerance than them, why let them go cold?
Some people might feel awkward or hesitant to do this because giving someone your jacket has been popularized especially in older media as a romantic flirtatious gesture. However, there is a difference between offering someone your jacket as a gesture of kindness and politeness, and giving someone your jacket as a flirtatious romantic gesture.
When done as a romantic flirtatious gesture it’s more standard to take the jacket and wrap it around the shoulders of the subject of your wooing. But when done just as a friendly polite gesture one just hands the extra jacket / cardigan / ect. to them and leaves it to them to put it on themselves.
Another way to differentiate between a romantic gesture and just being nice is that in a romantic gesture one doesn’t ask for the jacket back, and it is in the possession of the subject of their wooing for an indefinite amount of time.
With a friendly non-romantic gesture it’s only temporarily being loaned. So if you really want to be sure you’re not accidentally sending the wrong message when just trying to be nice, add a disclaimer such as “just get it back to me at the end of the movie / when we get back to the car / ect.” (in a friendly tone, not an aggressive or accusatory tone as you also don’t want to come across as accusing them of trying to steal your clothes)