Summer hat?

My FIL is in poor health and stays cold all the time. I made him a little toboggan/toque type hate for Christmas, and MIL says he basically only takes it off to go to bed.

However, with spring coming, he still wants to wear it, but she likes a lighter cotton hat will be better. Obviously, a plain cotton hat won’t be what she’s thinking of (too heavy and not enough give, etc.).

So…any ideas on a pattern (or just a good yarn for a basic hat pattern) for a cold,elderly man for summer???

something like this perhaps?
or this?

use a cotton or bamboo blend yarn. It’ll have more stretch/give then 100% of either.

Bamboo wicks away moisture so it will be cooler.