Its amazing to me how quickly climate can change with topography. One of my favorite things about road trips is to see that change happen at 60-70 mph...like driving into Bend, OR. You come out of the trees on Mount Hood into desert at the tree line so fast.
While hiking in Utah, we changed from one forest type at the top of the hike, into pinyon pine and juniper, into sagebrush in the matter of around 6 miles.
I've been backpacking in the heat and humidity before. The type where its too hot to sleep. I realized as I lay there, on my insulated camping mat, overheated from a day of carrying a heavy pack, that I was insulated from the ground. I laid down on the ground for a while and I cooled off to where I could sleep fine.
Worked in Death Valley in a canyon where the sun beat all day. It was april and 104 degrees in the shade. The ground in the shade should generally be a heat sink. Laying one the ground with max contact and minimum insulation can do wonders for heat buildup.
Running cold water over your head and neck for a literal minute or two will suck out a lotta heat, too. Many people will run it over their head enough to get their hair wet and stop.