Try a desert trick. When the air outside is dry and cooler than the air inside, hang a damp sheet in an open window. "That's what we do here in Death Valley," says Dale Housley, a ranger at Death Valley National Park. Incoming breezes are cooled by the evaporating water.
Block the sun. Closing curtains and blinds (ideally with sun-deflecting white on the window side) can reduce the amount of heat that passes into your home by as much as 45 percent, according to the U.S. Department of Energy.
2 of 12Monica Buck
Don't Blow Hot Air
Make a makeshift air conditioner. If it's hot but not humid, place a shallow bowl of ice in front of a fan and enjoy the breeze. As the ice melts, then evaporates, it will cool you off.
Give your A/C some TLC. Clean or replace the filter in room and central air conditioners about once a month during the summer. If you have central air-conditioning, have the ducts checked for leaks, which can reduce a system's efficiency by as much as 15 percent, according to the U.S. Department of Energy. Seal any cracks between a window unit and the frame with peelable caulking or a sealant strip. These steps help ensure good airflow and keep the coils cleaner, which means more efficient and more effective cooling.
3 of 12Monica Buck
Close It Down
Close the damper. While running any kind of air conditioner, shut your fireplace damper. An open one "pulls hot air into your house instead of sucking it out," says Tommy Spoto, a master chimney sweep at Chimney Chap, in Copiague, New York. "This is called flow reversal."
Close everything else, too. Whether the air conditioner is on or off, keep windows and doors shut if the temperature outside is more than 77 degrees Fahrenheit (most people start to sweat at 78). Whenever the outside air is hotter than the inside air, opening a window invites heat to creep in.
4 of 12Monica Buck
Give a Squirt
Spritz yourself. Keep a spray bottle in the refrigerator, and when the going gets hot, give yourself a good squirt. "It's all about thermal regulation," says John Lehnhardt, an elephant expert at Disney's Animal Kingdom, in Lake Buena Vista, Florida. "As the water evaporates, it cools you." While elephants wet their ears first by blasting water from their trunks, humans should begin with their wrists to quickly cool down the blood flowing through their veins.
Fan strategically. If the day's heat is trapped inside your home, try a little ventilation at night or when the temperature drops below 77. A window fan can help; the trick is to face the blades outside to suck warm air out of the house and pull cooler air in. "Kind of surprising," says Bill Nye, the Science Guy, a scientist, engineer, comedian, author, and inventor. "Having a fan blowing in is a good idea―but it's not as effective as one that's blowing out."
5 of 12Andrew McCaul
Vent a Lot
Run a fan and an air conditioner simultaneously. You can use the air conditioner at lower power and still feel cool if the fan is blowing over you. That's because the air conditioner removes humidity from the air while the fan helps evaporate sweat and moves heat away from your body. (Note: Fans don't cool a room; they just make people feel cooler, so shut them off before you leave.)
Turn on the vent in the bathroom. When taking a shower, be sure to use the vent fan: It helps sticky moisture escape.
6 of 12Mark Lund
Observe Key Notes
Let your computer take a nap. Set it to go into low-power "sleep" mode if you are away from it for more than 10 minutes and it will give off less heat. When you're finished for the day, shut the machine down completely. Despite what some IT guy may have told you years ago, properly shutting down and restarting modern-day computers won't put undue strain on the hardware. And forget about working with a computer on your lap―it's too darn hot. "That's why they changed the name from laptop to notebook," says Justin M. Solomon, a 19-year-old undergraduate at Stanford University who took first place in computer science at the 2005 Intel International Science and Engineering Fair.
Wick while you work. To keep yourself cooler when computing, plug a Kensington FlyFan ($40, amazon.com) into a USB port on your machine. The fan's flexible neck lets you direct the breeze to your sweaty brow.
7 of 12Monica Buck
Try Air Drying
Skip the drying cycle on the dishwasher. Instead, leave the door open to let the dishes dry. And put off using the dishwasher until evening, when the air is cooler. Or simply wash your dishes the old-fashioned way: by hand.
Dress right. Wear one of the widely available synthetic fabrics designed to wick away sweat and that sticky feeling (examples include Coolmax and Nano-Tex); they're not just for athletes anymore. If you prefer cotton, make it thin, light colored, and, most of all, loose. "The best thing is to have sweat evaporate directly from skin to air," says Larry Kenney, a professor of physiology and kinesiology at Pennsylvania State University, in University Park. "The next best thing is for the sweat to move quickly from your skin to clothing and then evaporate. Loose, billowy clothes allow air movement next to the skin and help with evaporation."
8 of 12Kate Powers
Lose (or Choose) the Hot Stuff
Shuck your shoes. As the sweat on your feet evaporates, it cools the skin and the blood in your feet. Blood vessels then whisk that blood to other parts of the body, so "you're getting a greater sensation of coolness," says Donald R. Bohay, M.D., a member of the American Orthopedic Foot & Ankle Society.
Spice it up. As people who live in scorching climates, such as those of Mexico and India, know well, eating hot stuff can cool you down. "Chili peppers contain capsaicin, a chemical compound that helps us to perspire more readily," says Rick Bayless, the James Beard Award-winning chef of Frontera Grill, in Chicago. When this sweat evaporates, you experience brief relief.
9 of 12David Prince
Swig often. To replace the moisture that you lose as you perspire, be sure to drink. As you lose water to dehydration, your body temperature rises, so replacing fluids is essential to keeping cool. Avoid beverages that contain alcohol, caffeine, or lots of sugar, which are dehydrating. "Also opt for hydrating foods," says Deena Kastor, a marathon runner and an Olympic bronze medalist. "Try a smoothie for lunch, and add more fruits and vegetables to all your meals. Watermelon has the greatest water content of any food out there."
Eat light. There's a reason we reach for salads in the summer. They're easier to digest than, say, a fatty hamburger, which leaves you feeling sluggish in the high heat. Instead, go for fruits and vegetables, which are watery and help keep you hydrated (and cooler), says Robert Kenefick, a physiologist at the U.S. Army Research Institute of Environmental Medicine, in Natick, Massachusetts, which studies the effects of extreme climates on soldiers' bodies.
10 of 12Anna Williams
Opt for a Shutdown
Give your oven a summer vacation. If you cook, use the stovetop, the microwave, or a barbecue. "Grill some extra vegetables when you're making dinner," says Deborah Madison, author of Vegetable Soups From Deborah Madison's Kitchen (Broadway, $20, amazon.com). "The next day, mix them with a little Feta cheese and olive oil for a great, cool snack."
Shut the lights. Or change the bulbs: Long-lasting compact fluorescent bulbs produce about 70 percent less heat than standard incandescents.
11 of 12David Tsay
Take Some Dry Measures
Give the clothes dryer a break, too. Hang a clothesline and let your towels and sheets flap in the breeze. "They smell wonderful," says Paul Hooker, whose company, Sferra, sells sheets made in Italy, where, he adds, almost everyone hangs them out to dry.
Make a "cold compress." Fill a cotton sock with rice, tie the sock with twine, and freeze it for two hours before bedtime. Then slide it between the sheets. Rice retains cold for a long period because it's dense and starchy, says Jim Hill, Ph.D., an associate dean of the College of Agricultural and Environmental Sciences at the University of California at Davis.
12 of 12Thayer Allyson Gowdy
Escape. Relax with A Winter's Tale, The Call of the Wild, Doctor Zhivago, or Smilla's Sense of Snow. "Reading about cold can take your mind off the thermometer, evoking one's own experience of ice and snow," says Walter A. Brown, a clinical professor of psychiatry at the medical schools of Brown and Tufts Universities and an expert in the placebo effect. "It's also a bit of self-hypnosis. Sometimes when I shower and the water is cold, I tell myself it's hot and I can make myself believe it." You can save that last insight for another season entirely.