I'm pretty bad in the heat. Years ago, I did an intense 7 day cycle tour over the Snowy Mountains (southeastern Australia), and got heatstroke on the first day. (Writeup here:
https://steventuring.wordpress.com/2...owy-mountains/ ) The forecast for the week was constant 37C (99F) every day in the valley (fortunately, a few of the days were at much higher elevation).
For me, what I've learnt from that and since are:
- drink a lot before starting (constant small sips from the moment I get up)
- start very early, and nap during the heat of the day, if possible
- drink plenty with electrolytes
- wear a wet travel towel under my helmet (I call it "towel of life"), refresh it as often as possible (very easy to just pour water in through the helmet vents)
- if passing any rivers/creeks, get off the bike for a full soak. I go in fully clothed, shoes and all. Obviously you eventually dry out, but usually the first 15 minutes is bliss, and the next 15-30 minutes is pretty comfortable.
- cancel if the forecast is too high. (There are limits to what I can safely ride in. I generally won't ride in >35C, and I'm pretty iffy about anything over 30C)