Even on a crisp November day, your body has to work at staying cool. That's because your body generates heat as a byproduct of all its metabolic processes. If you retained that heat, your temperature would shoot up dramatically. To prevent that, your body is constantly shedding heat. The body dissipates most of its excess heat through your skin. But to succeed at that, two conditions must prevail. First, your circulation must be able to pump plenty of blood to your skin. Second, the air must be cooler than your blood, so you'll give up heat by conduction (the direct transfer of heat from a warm body to a cooler environment); add a cooling breeze, and you'll also lose heat by convection (heat exchange enhanced by air flow).
Under normal circumstances, conduction is an efficient mechanism for heat loss; that's why you take off your shirt in summer and put on a sweater in winter. But when the air temperature approaches body temperature, or when exercise sends your body's heat production soaring, conduction won't do the trick. Now evaporation kicks in; you'll sweat profusely, and as sweat evaporates, it will carry away your excess body heat. But as humidity climbs, evaporation slows, then stops.
Heat-related illnesses result from an imbalance between man and nature. Nature contributes high air temperatures, high humidity, the radiant energy of sunlight, and still air. You can't do much to change nature, but you can control the human elements that contribute to heat illnesses; undue exposure to sun and heat, unwise exercise, inappropriate clothing, and dehydration head the list.
Sweating is the body’s mechanism for self-cooling, but plenty of water is needed to give it something to work with. Recommendations vary between drinking two to four glasses of water every hour in excessive heat. Do not wait until you are thirsty to hydrate your body.
Pay attention to what you eat
Diet affects how you can manage your body’s response to high temperatures. Eat less salty food and protein, which produce metabolic heat that causes water loss. Eat more fruits and vegetables and smaller, frequent meals. Alcohol consumption can also increase the effect of heat.
Wear loose, lightweight, light-colored clothing and take cool showers or baths
“If you can pour water on exposed skin, that is going to allow your body to cool down,” Mr. Schichtel said. Invest in good quality bedding with a high cotton count to ensure what you’re sleeping in is as breathable as possible. “The natural fibres allow air to move freely and circulate through the fabric, which helps to keep you cooler through the night,” says Robinson. The same rule applies for sleep wear – the higher the cotton count on your pyjamas, the better. Try Desmond & Dempsey’s Medina Short Pyjama Set.
Invest in A cooling system
Electric fans will go only so far; air-conditioners are better for keeping your body cool. If you don't have air conditioning don't buy a cheap fan. The cheaper the fan, the more likely you are to hear it, which isn’t conducive to good sleep. Dyson’s Pure Cool Me delivers focused airflow, rotates and can be set on a timer.
Learn the signs of heat stroke and heat exhaustion
The C.D.C. lists some of the signs as dizziness, a rapid pulse, nausea, headache and fainting. But symptoms can vary. Those having heat stroke, which is potentially fatal, might have a rapid but strong pulse, while those with heat exhaustion might have a rapid but weak one. Seek out indoor activities, particularly during the hottest part of the day. The sun’s peak hours are generally 11 a.m. to 4 p.m. “There are times you are going to be in the sun, but if you can avoid as much direct sunlight as possible, it is better,” Mr. Schichtel said. Wearing a hat protects you from direct sun; sunburns affect your body’s ability to cool down and can make you dehydrated, according to the C.D.C.
Don't exercise when it's hot or humid
If it's humid and above 80° to 85°, jump in a pool or work out in an air-conditioned gym. If you exercise outdoors, do it in the early morning or evening. Slow down; walk instead of jogging or use a cart instead of walking the golf course. Take breaks and quit early.
Above all, listen to your body. Muscle cramps, fatigue, weakness, nausea, impaired concentration, confusion, lightheadedness, labored breathing, chest discomfort, and a rapid or erratic pulse can all be signs of trouble. Heed your body's warning signals; if you feel even a little ill get to a cool place, drink plenty of cool water, and be sure help is available if you don't improve promptly.