Usually the summer here in the UK is warm, but not over hot. We haven't really had protracted periods of sunshine in recent summers.
And I'd almost forgotten what hot summers bring out, can you remember?
Hot summers bring out summer clothes. For men this just seems to be t-shirts and jeans, and in cases of extreme heat shorts, or cut-offs.....and no, I'm not going to say anything about men's legs. Although, it is obvious that some of them are usually wrapped up in long pants, and resemble well cultivated celery.
No...my observation is that many women don't seem to possess underskirts, or for that matter think about their undergarments, mainly their knickers. The other day I saw a woman in a beautiful white linen skirt, it had some very pretty applique on it and some heavy cotton lace fastened to the lower edge of the skirt, it really was a pretty skirt, then I noticed that she mustn't have been wearing an underskirt, as you could clearly see her knickers, and what is more, they were black, so really did show. Given the person, I don't think she knew that her pants were visible through her skirt, as I'm sure she would have been mortified. It wasn't a case of visible pantie line, but visible pants
Other things I have seen when walking around are skin tight dresses clinging to the wearer's body, as they should, but to such an extent that the underwear might as well have been worn over the top. Skirts riding up the wearer's legs is another thing I've seen, both these would be prevented by wearing an underskirt, but I'm guessing that the women wearing these dresses, etc might normally wear trousers or jeans most of the time, and didn't even consider that an underskirt might be necessary. Or is it just a generational thing, as I have always worn one, and when my daughter was younger she did, but she "lives" in trousers.