If you've got a well and your well water is always significantly below body temperature one thing that might be worth considering is installing a hand pump. You

If you've got a well and your well water is always significantly below body temperature one thing that might be worth considering is installing a hand pump. You could then at least draw a bath and sit in the tub to remain cool. That works by contact with something colder than you. It does not rely on evaporation and so is not affected by high humidity.