The body definitely adjusts to heat and cold. It takes a while, but I know it happens, so I am convinced the subconcious regions of the brain which control things like breathing, blood flow, digestion, release of sugar and adrenalin, can learn from experiences and adjust the response of these systems.
Tests with people who have repeatedly endured extreme cold, like Navy divers and trappers in the North, have shown that their bodies ramp up the burning of sugars and fats to keep the core temperature much higher than normal people, so that they can survive in water below 40 degrees for more than an hour, and still think and function.
The same is true with heat and humidity. The body has to learn to sweat and to regulate its temperature.
