A few years ago I was out shooting at Patar (Southern Turkey) with a friend from Yorkshire who lived nearby in Fethiye, it was over 40ºC a round the 43-44ºC mark so about 110ºF by the time we shot there around midday, we'd already been out for at least 4 hours but up in the mountains earlier where it's much cooler. The air conditioning in the car helped a little after but was just all the windows open
I was shooting LF but I have a small light weight set for conditions like this to avoid carrying a lot of weight/bulk, although I did have my 210mm Symmar with me. I've gone out in similar conditions since but never particularly far from a car and plenty of water, the last time was in Cyprus two years ago.
UV factor didn't worry me, I'd build up natural protection working by a pool side early in the year (I was working on some books). So by July/August the hottest/sunniest period I could be out all day and not burn. Now unless already tanned I'm careful.
There's something odd about how we cope with heat here in the UK/Europe we are used to quite large fluctuations in a day, I noticed while living in Turkey that locals felt cold in the late Autumn and would have coat, scarves, hats etc while I'd be in a T-shirt and there were still the odd German women topless on the beach.
I'm luck as long as I keep my darkroom door closed in this heat it stays cool, as my dog appreciates

That's only because I've insulated itwell - walls, floor, ceiling, door etc so it's easy to heat in the Winter

In Turkey we use air conditioning when excessively hot.
Ian