It's not the heat that's the problem it's the shock to the system of the temperature suddenly doubling down here in Devon.
Worked Tuesday, drank loads, kept my hat on - early night as I felt rough. Couldn't sleep, up at 11pm shaking like a leaf and freezing cold. More drink and two duvets and I managed to go to sleep. Couldn't work yesterday.
Great day today - hot sun - drank loads, worked loads - feel great !!
Shock over now & shouldn't have any problems for the rest of the summer but every year I get caught out when the temperature jumps - whatever I do.