The CDC offers the following prevention tips for staying cool and safe when the mercury rises.
Drink plenty of fluids
During hot weather you will need to increase your fluid intake, regardless of your activity level. Don't wait until you're thirsty to drink. During heavy exercise in a hot environment, drink two to four glasses (16-32 ounces) of cool fluids each hour.
Avoid alcoholic and sugary drinks
Don't drink liquids that contain alcohol, or large amounts of sugar -- these actually cause you to lose more body fluid. Also avoid very cold drinks, because they can cause stomach cramps.
Replace salts and minerals
Heavy sweating removes salt and minerals from the body. These are necessary for your body and must be replaced. A sports beverage can replace the salt and minerals you lose in sweat. However, if you are on a low-salt diet, talk with your doctor before drinking a sports beverage or taking salt tablets.
Wear appropriate clothing
Wear as little clothing as possible when you are at home. Choose lightweight, light-colored, loose-fitting clothing. If you must go outdoors, protect yourself from the sun by wearing a wide-brimmed hat (also keeps you cooler) along with sunglasses.
Don't forget the sunscreen
Avoid sunburn and keep your skin safe by putting on sunscreen of SPF 15 or higher (the most effective products say "broad spectrum" or "UVA/UVB protection" on their labels) 30 minutes prior to going out. Continue to reapply it according to the package directions.
Schedule outdoor activities carefully
If you must be outdoors, try to limit your outdoor activity to morning and evening hours. Try to rest often in shady areas so that your body's thermostat will have a chance to recover.
If you are not accustomed to working or exercising in a hot environment, start slowly and pick up the pace gradually. If exertion in the heat makes your heart pound and leaves you gasping for breath, stop all activity. Get into a cool area or at least into the shade, and rest, especially if you become lightheaded, confused, weak or faint.
Stay cool indoors
Stay indoors and, if at all possible, stay in an air-conditioned place. If your home does not have air conditioning, go to the shopping mall or public library -- even a few hours spent in air conditioning can help your body stay cooler when you go back into the heat.
Use a buddy system
When working in the heat, monitor the condition of your co-workers and have someone do the same for you. Heat-induced illness can cause a person to become confused or lose consciousness.
Monitor those at high risk
Although anyone at any time can suffer from heat-related illness, some people are at greater risk than others. Those groups include infants and young children, people 65 years of age or older, and people who are overweight. Visit adults at risk at least twice a day and closely watch them for signs of heat exhaustion or heat stroke.
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 have a greater tolerance for heat 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.
Do not leave children in cars
Even in cool temperatures, cars can heat up to dangerous temperatures very quickly. Even with the windows cracked open, interior temperatures can rise almost 20 degrees within the first 10 minutes. Anyone left inside is at risk for serious heat-related illnesses or even death. Children who are left unattended in parked cars are at greatest risk for heat stroke, and possibly death.
Use common sense
Avoid hot foods and heavy meals -- they add heat to your body. Dress infants and children in cool, loose clothing and shade their heads and faces with hats or an umbrella. Provide plenty of fresh water for your pets, and leave the water in a shady area.
Watch out for heat-related illnesses
Doing too much on a hot day, spending too much time in the sun or staying too long in an overheated place can cause heat-related illnesses. Know the symptoms of heat disorders and overexposure to the sun, and be ready to give first aid treatment.
Listen to local news and weather channels or contact your local public health department during extreme heat conditions for health and safety updates