Adjust to the environment:
Be aware that any sudden change in temperature,
such as an early summer heat wave, will be stressful
to your body.
You will tolerate the heat better if you limit your
physical activity until you become accustomed to the
heat.
If you travel to a hotter climate, allow several days to become acclimated before attempting any vigorous exercise, and work up to it gradually.
Pace yourself. If you are not accustomed to working or exercising in a hot environment, start slowly and pick up the pace gradually.