I love the sun, and heat. But taking my shirt off and getting lots of full-on sun even for just five or ten minutes makes me want to go inside and take a nap. That’s what I just did.
I almost never can nap during the day. Wish I could more often, but it just ain’t happening. Then a little time shirtless in full, hot sun and I’m overcome with a tired lethargy; gotta sleep!
If it’s hot at night, I can’t sleep, so it’s not just the heat. It seems to be exposure to the sun, then shade that triggers a sleep reflex, hot or not.