How do we do it???

Ideally, a bottle of water, a bottle of electrolyte solution, another bottle of water for your head. And if you keep moving, the evaporative cooling works, somewhat.

That said, I whined recently about having trouble with heat exhaustion....

I think I could easily handle humidity somewhere around 50% and a balmy 85 degrees! That would be terrific riding weather.

Just don't give me cold, nooooooo
I like x-country skiing, but biking in the cold drizzly weather, noooooo