On cold days, blood is kept away from the skin to keep the body from losing heat. On hot days, blood is kept close to the surface of the skin to allow heat to escape. In addition, perspiration is released. Perspiration evaporates, pulling heat away from the body.
On extremely hot days, very little heat escapes the body, since the outside air is as warm (or warmer) than the blood. On very humid days, evaporation is slowed dramatically, making perspiration ineffective. When the body is unable to rid itself of heat, heat illnesses (heat exhaustion or heat stroke) can develop. People have a higher chance of becoming dehydrated as heat and humidity increase.
FEMA and the National Weather Service provide tips for staying safe on hot, humid days:
- Stay indoors when possible and limit exposure to the sun. Seek shade when outdoors. Protect your face and head by wearing a wide-brimmed hat.
- Moving air increases evaporation of perspiration and helps cool the body faster. Use fans and air conditioning to circulate air, if possible. This is even more important on days with high humidity.
- Heat rises, so stay on the lowest floor possible, unless air conditioning is available.
- Spend the hottest part of the day in public buildings with air conditioning--libraries, movie theaters, shopping malls--if you cannot keep your home cool.
- Drink plenty of water. Persons who have epilepsy or heart, kidney, or liver disease; are on fluid-restricted diets; or have a problem with fluid retention should consult a doctor before increasing fluid intake.
- Avoid alcoholic beverages on hot days. Alcohol causes increased urine production, which may lead to dehydration.
- Eat well-balanced, light, and regular meals. Drinking lots of water without eating can lead to possible water intoxication. Proper food intake should help avoid this. Do not use salt tablets unless directed to do so by a physician.
- Wear loose, lightweight, and light-colored clothing. Cover as much skin as possible.
- Check on family, friends, and neighbors who do not have air conditioning and who spend much of their time alone.
- Never leave children or pets alone in closed vehicles, even on days with relatively low temperatures.
- Avoid exertion during the hottest part of the day. Share work with others in extreme heat, and take frequent breaks.
" Extreme Heat: A Prevention Guide to Promote Your Personal Health and Safety." 15 Aug 2006. Emergency Preparedness & Response. CDC. 27 Jul 2007