Heat hits people in different ways. I used to race Karts in Europe and have raced in temps of 105F. Big problem was not the heat but the Humidity. Only way to beat that in those days was plenty of water and Salt Tablets.
Last Sunday I was on a ride- Either riding or queuing or waiting for friends for 6 hours in 85 F temp. Did not bother me at all. Mainly because there was low humidity and a bit of a breeze. Mind you the number that were affected by the heat was phenominal. You could see them flaked out by the road.
As I said- Heat hits people in different ways- Try getting to a Sauna to get accustomed. Even if it does not work- A sauna is still enjoyable.
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How long was I in the army? Five foot seven.
Spike Milligan