If you spend a lot of time outside in the summer, dont wear a hat or sunscreen, and are a white person, you will learn about the savagery of the dreaded sunburn on your head. It's awful. You can feel your heartbeat in the top of your head and it hurts to raise your eyebrows. If you shave your head and keep it shaved, get a nice collection of hats to protect you from the sun.

Oh gods this one.

Also putting sunscreen on your head is not something you've ever trained for, but if you don't like hats you'll really have to go to town there, your scalp has pretty much never seen the sun, even if you're a very pale person in general your scalp is worse than any other part of your body.

You'll also realize how much your hair keeps the top of your head warm. If it's winter and even mildly chilly in your house or outside, the top of your head will be cold. I have a vast assortment of thin gauge beanies I wear near constantly around the house in winter. I fall asleep with them on sometimes.

That one really depends whether you tend to "run cold" or "run warm" (and which climate you live in).

What surprised me was the opposite: in the summer winds feels way less cooling, aside from keeping sweat out of your face, hair wicking away sweat means there's a much greater surface area of sweat exposes to the wind, so the sweat evaporates much faster and cools your head down. Without that you just have a layer of warm sweat on your head, there's less evaporation and it's only the top layer which evaporates not the bottom layer that's against your skin. Here again it depends on the weather and your personal sensibilities (and amount of sweating), but that's one more thing a bandana or wicking skullcap helps with.