Your body loses heat in four ways: radiation from your skin (about 60% of total heat loss), evaporation of sweat (about 22%), convection from air moving over your skin (about 15%), and a small amount through direct contact with cooler surfaces. Every strategy for staying cool works by boosting one or more of these pathways. Here’s how to make each one work harder for you.
How Your Body Cools Itself
When your core temperature rises, two things happen automatically. Your sweat glands ramp up production, and blood vessels near your skin dilate to push warm blood toward the surface, where heat can escape. Every gram of sweat that evaporates pulls about 0.58 kilocalories of heat from your body. Even when you’re not noticeably sweating, your skin and lungs lose 600 to 700 mL of water per day through passive evaporation.
This system works well in dry heat but struggles in humidity. When the air is already saturated with moisture, sweat can’t evaporate efficiently, so it drips off instead of cooling you. That’s why 90°F with 80% humidity feels far worse than 100°F in a desert. Anything you can do to help sweat evaporate faster, like moving air across your skin or wearing the right clothing, directly improves your body’s cooling engine.
Drink Enough, and Add Electrolytes
Sweating can reach 3 to 4 liters per hour during intense exercise in the heat, and total daily losses can hit 10 liters. You can’t cool down if you’re running low on the fluid your body needs to produce sweat. The National Institute for Occupational Safety and Health recommends drinking 24 to 32 ounces (about 710 to 950 mL) of water per hour during heat exposure. That’s roughly a standard water bottle every 30 to 45 minutes.
Plain water is fine for shorter periods, but if you’re sweating heavily for more than two hours, adding electrolytes helps your body hold onto fluid rather than flushing it through. You don’t need a specific formula. A sports drink, a pinch of salt in water, or electrolyte tablets all work. The goal is replacing the sodium and potassium you’re losing in sweat so your hydration actually sticks.
Ice Slurry Beats Cold Water
Drinking something cold pulls heat from your core as your body warms the liquid to body temperature. But not all cold drinks are equal. Ice slurry, basically a slushy consistency of crushed ice and water, lowers core temperature significantly more than cold water at the same volume. The ice melts as it passes through your digestive tract, absorbing extra heat energy during the phase change from solid to liquid. In one study comparing ice slurry to room-temperature beverages, the slurry group had measurably lower core temperatures that persisted well into subsequent physical activity.
If you’re heading out for a run, working outdoors, or just trying to cool down fast, blending ice into a slushy drink is one of the simplest and most effective internal cooling tools available.
Where to Apply Cold for the Fastest Relief
The common advice to put ice on your wrists and neck has some logic behind it: blood vessels run close to the surface there, so cold contact can cool circulating blood. But the actual surface area involved is small, and research shows the results are underwhelming. A study in Frontiers in Sports and Active Living found that single-hand cooling (which targets the palm’s specialized blood vessels) produced no significant temperature reduction compared to doing nothing at all.
What did work was covering more skin. An ice vest covering the torso cooled core temperature nearly twice as fast as hand cooling alone, at a rate of about 0.025°C per minute versus 0.017°C per minute. The takeaway: cooling a larger area of skin beats targeting a single pulse point. If you don’t have an ice vest, draping a wet towel across your chest, back, and shoulders will cover more surface area than holding ice cubes against your wrists. A cold, wet shirt works on the same principle.
Choose the Right Fabric
Fabric choice matters more than most people realize. The two things to look for are breathability (how easily air passes through) and moisture management (how quickly sweat moves away from your skin and dries).
- Linen is one of the most breathable fabrics because its fibers are large and typically woven loosely. It’s excellent for casual, low-activity situations. The downside: it absorbs moisture rather than wicking it, so it gets heavy and clings if you’re sweating hard.
- Cotton is similarly breathable and soft but shares linen’s weakness. It soaks up sweat and stays wet, which can actually feel cool in a breeze but becomes uncomfortable quickly.
- Nylon and polyester wick moisture and dry fast, making them the better pick for exercise or physical work. Breathability varies by weave, so look for lightweight, loosely knit versions rather than thick athletic compression gear.
- Silk is lightweight and breathable but fragile and not moisture-wicking, making it impractical for anything beyond sitting in the shade.
Lighter colors reflect more solar radiation. Loose fits allow air to circulate between the fabric and your skin, boosting convective cooling. A loose, light-colored polyester shirt is hard to beat for active use in the heat.
Use Fans Wisely
Electric fans cool you by speeding up sweat evaporation and increasing convective heat loss. But there’s a limit. The World Health Organization has advised against fan use when ambient air temperature exceeds 95°F (35°C), because at that point the fan is blowing air that’s hotter than your skin, essentially basting you in hot air and accelerating dehydration.
More recent analysis suggests fans can still help above 95°F if humidity is moderate, because the moving air still boosts evaporation. The practical rule: if the air feels like a hair dryer and you’re not sweating much, the fan is working against you. If you’re sweating and the air movement helps that sweat dry, the fan is still useful. Misting your skin with water while using a fan supercharges evaporative cooling, even in very hot conditions.
Keep Your Bedroom Cool Enough to Sleep
Your core temperature naturally drops at night to initiate sleep, and a warm room fights that process. The Cleveland Clinic recommends keeping your bedroom between 60 and 67°F (15 to 19°C). Anything above 70°F starts to interfere with sleep quality. For babies and toddlers, the ideal range is slightly warmer, between 65 and 70°F.
If you can’t get the room that cool, focus on what touches your skin. Sleep on cotton or linen sheets, which breathe better than polyester. A damp towel draped over a fan creates a simple evaporative cooler. Sleeping with a thin, wet sheet can also drop your skin temperature enough to fall asleep on hot nights. Avoid heavy blankets, memory foam (which traps heat), and eating large meals close to bedtime, which raises your metabolic heat output.
The Spicy Food Paradox
Eating spicy food in hot weather sounds counterintuitive, but there’s a reason cultures in the hottest parts of the world built their cuisines around chili peppers. Capsaicin, the compound that makes peppers hot, activates the same heat-sensing receptors in your mouth and gut that respond to temperatures above 109°F (43°C). Your brain interprets this as a heat signal and triggers cooling responses: you sweat more, and blood flow to your skin increases. The food isn’t actually raising your temperature. It’s tricking your thermoregulation system into turning on its cooling mechanisms.
This only helps in conditions where sweat can evaporate. In high humidity, the extra sweating may just leave you damp and uncomfortable without much cooling benefit.
Recognizing When Cooling Isn’t Enough
Heat exhaustion shows up as heavy sweating, cold and clammy skin, a fast but weak pulse, nausea, muscle cramps, and dizziness. Your body is still trying to cool itself but struggling to keep up. Moving to a cool place, drinking water, and applying cold compresses to large skin areas will usually resolve it.
Heat stroke is a medical emergency. The hallmarks are a core body temperature of 103°F or higher, skin that’s hot and red (and sometimes dry, meaning sweating has stopped), a fast and strong pulse, confusion, and possible loss of consciousness. The critical difference from heat exhaustion is that the body’s cooling system has essentially failed. This requires emergency medical care immediately.