In article 5a2dc87e-724e-464c-b75b-ba366612e867
@r4g2000prm.googlegroups.com, says...

This past weekend in the woods was beautiful except for one thing.
Although it was only 88 degrees, I felt as if I was overheated from
tromping thru the woods. Most of the time I was wearing a caving
helmet and I found that when I took it off I was much more comfy. In
the past, I have noticed I cannot wear any sort of hat in anything but
winter weather otherwise I overheat. Instead I wear a visor to block
the sun from my eyes. I have concluded that most of my overheating is
because my head gets too warm. It is no longer a matter of simply
being uncomfortable but has become a serious safety issue for me.
So, how much would getting a crew cut haircut help? Generally, I
think having some hair prevents sunburn. Those of you who have little
hair, how much do you burn? Does sunscreen help? Would a bandanna
soaked in cold water help. In the past, I have dunked a hat in water
to cool by evaporation and it helps some.

Well, I have a leather (Aussi Outback) hat I usually wear but when it
gets hot, I have a woven (fake reed, probably nylon) Outback that lets
some air come off the head.. It seems to do the trick nicely letting out
the moisture and heat the solid leather hat keeps in but still is enough
to keep the heat off and the sun off of your face, back, neck and
shoulders. BTW, both of the hats are black, I am sure white would even
be better. An Outback is similar to a cowboy hat but with a much
narrower brim... Just for reference.

As to longer hair, I have it on the back and sides, I guess you could
call it a mullet although when I was rockin' in the 80's we called it a
shag. Either way, the hair up top and front is only 2-3 inches long and
cut to stay out of my face which helps a lot in the heat too...