I don't know what to tell you about the humidity - but on my Telluride/Moab ride, all our days were well above 90 and I got through it by wetting my head and my Cool Wings or my arm coolers. The evaporation made a huge difference. It was a very dry heat though - I would guess humidity below 20.

Go early in the day if you can, keep your rides short, maybe do intervals if you're hoping to maximize training. But if you're just riding for fun - keep it fun.

Veronica