The job I had for over 25 yrs put me in some hot places 130 degree plus at times I agree with Jo runner you can acclimatize to heat I did. I know I did Mc Laughlin last July in 100 degree temps and only used about 2 and half liters of water. A very hot dry climb.
We were taught about dehydration a lot of breaks water Gatorade electrolyte pills, no soda or Caffeine not all followed this.
I know as I worked with the older guys blood pressures meds statins raised caution. I've been lucky my blood pressure and blood work still are excellent.
Now taking early retirement it will be interesting to see how it affects me.
Some of my young apprentices got a bit loony when they thought I was full of BS sometimes the next day they looked like a truck hit them and were worthless.
Its not a joke.
Nobody ever tarped it on the job tho