Howard Rosenberg, UC Berkeley agricultural personnel management specialist (howardr@are.berkeley.edu), points out ten ways how heat affects the body:

1. Bodily functions depend on blood circulation and many chemical reactions that occur best at about 98.6 degrees. The body has natural ways of gaining or losing heat to maintain this “normal” temperature.

2. Your own body is the main source of heat that may stress you. When your body is active, it usually generates more heat than it needs and, therefore, has to release some.

3. The harder you work, the faster you generate heat, and the more your body has to get rid of heat. Hot weather and high humidity increase your risks by slowing the transfer of heat to the air around you.

4. When you produce heat that raises internal temperature, your heart rate increases and vessels expand to bring more blood to the outer layers of skin, where the heat is released.

5. If excess heat is not released fast enough this way or the surrounding air is warmer than your body, your sweat glands go to work. They draw water from the bloodstream to make sweat that carries heat through pores and onto the skin surface, where it evaporates and releases the heat.

6. When more blood goes toward your body surface for cooling, less is available to serve your muscles, brain and other internal organs. Prolonged sweating draws a lot of water from the bloodstream, further reducing its capacity to deliver nutrients, clear out wastes, lubricate joints and cool you later.

7. If your body continues to lose fluid, you are likely to experience increasingly severe symptoms of "heat illness."

8. The best way to reduce your heat stress risks while working is to steadily replenish the water you lose as sweat. Drinking small amounts frequently is more effective than large amounts less often.

9. Relying on thirst as a signal to drink is dangerous. Most people do not feel thirsty until their fluid loss reaches two percent of body weight and is already affecting them.

10. If you notice heat illness symptoms, rest to stop generating heat, get fluids and tell your supervisor as soon as possible.