How can older people wear flannel in summer?

I was driving today and I kept seeing older men in long flannel shirts and jeans today mowing the lawn, weed-eating, and working in their yards. It is 95 degrees outside and the sun is beating down.

I know that people become more cold natured (usually) when they start to age but I don’t understand how they can stand wearing this clothing in such heat.

So i am wondering is it just them becoming more cold natured or is it something else that contributes to this clothing choice? I’ve been puzzled about this for years so all answers would be greatly appreciated.