Staying safe and comfortable in extreme heat comes down to managing two things: your body’s internal temperature and your environment. Your body starts suffering cellular damage when its core temperature rises above about 107°F (42°C), but you’ll feel the effects of heat long before that point. Here’s how to keep cool, recognize danger signs, and make smart choices when temperatures climb.
How Your Body Handles Heat
Your brain’s hypothalamus works like a thermostat. When it senses rising core temperature, it triggers two main cooling responses: increased blood flow to the skin (so heat can radiate outward) and sweating (so evaporation can pull heat away). In a warm environment, your body narrows the temperature gap between your core and skin surface by pushing more blood toward the surface. This is why your face flushes and your veins look more prominent on hot days.
These systems work well under normal conditions, but they have limits. High humidity slows evaporation, making sweat less effective. Dehydration reduces the volume of blood available for cooling. And certain medications, health conditions, or simply being unaccustomed to the heat can impair the process entirely. Understanding these limits is what separates mild discomfort from a medical emergency.
Stay Hydrated Without Overdoing It
OSHA recommends drinking at least one cup (8 ounces) of water every 15 to 20 minutes when you’re active in the heat, even if you don’t feel thirsty. Thirst is a lagging indicator. By the time you notice it, you’re already mildly dehydrated. However, there’s an upper limit: don’t exceed 48 ounces (about 1.5 quarts) per hour. Drinking too much water too fast dilutes the sodium in your blood, which can cause a dangerous condition on its own.
For prolonged sweating lasting several hours, sports drinks can help replace lost electrolytes. Salt tablets are generally not recommended unless a doctor has specifically told you to take them. Most people can restore electrolyte balance through regular meals, so eating normally on hot days matters more than you might think. Skip the alcohol, which increases sweating and impairs your body’s ability to regulate temperature.
Cool Your Space Without Air Conditioning
If you’re relying on fans, placement matters more than fan size. The most effective strategy is cross-ventilation: place intake fans on the cooler side of your home (typically north or east-facing windows) and exhaust fans on the hotter side (south or west-facing windows). This pulls cooler air in while pushing hot air out, creating a continuous flow through your living space.
A few additional tactics help significantly. Hang damp towels or sheets in front of a fan to mimic evaporative cooling. Close blinds and curtains on sun-facing windows during the day, since direct sunlight through glass can raise a room’s temperature dramatically. Cook outside or eat cold meals to avoid adding heat from your stove or oven. If your home becomes dangerously hot, public libraries, malls, and designated cooling centers offer free relief during heat waves.
Give Your Body Time to Adjust
Heat acclimatization is a real physiological process that takes 7 to 14 days of gradually increasing exposure. If you’re new to working or exercising in the heat, start with no more than 20% of your intended duration on the first day, adding roughly 20% each day after that. If you’ve been in similar heat before and are just returning after a break, you can ramp up faster: 50% on day one, 60% on day two, 80% on day three, and full exposure by day four.
During acclimatization, your body learns to sweat earlier, sweat more efficiently, and maintain a lower heart rate at the same workload. Skipping this process is one of the most common reasons people collapse in the heat during the first warm stretch of summer or after arriving in a hotter climate.
Recognize the Warning Signs
Heat illness exists on a spectrum, and catching it early makes all the difference.
Heat exhaustion is the body’s distress signal. Symptoms include heavy sweating, headache, nausea, dizziness, weakness, irritability, thirst, and decreased urine output. Body temperature is elevated but still below the danger zone. If you or someone near you shows these signs, move to a cool area, drink water, and apply cold compresses. Most people recover within 30 minutes to an hour with rest and cooling.
Heat stroke is a medical emergency. The hallmarks are confusion, slurred speech, altered mental status, or loss of consciousness, along with very high body temperature. Contrary to popular belief, skin can be either hot and dry or still sweating profusely during heat stroke. The key distinction is the mental state changes. If someone seems confused, disoriented, or unresponsive in the heat, call emergency services immediately and begin cooling them aggressively with ice, cold water, or wet sheets while waiting.
Heat rash is less dangerous but very common. It appears as red clusters of small blisters, usually on the neck, upper chest, groin, under the breasts, or in the creases of your elbows. It’s caused by trapped sweat in humid conditions. Keeping skin dry, wearing loose clothing, and using powder on affected areas typically resolves it.
Medications That Make Heat Riskier
Several common medications interfere with your body’s ability to cool itself, and many people taking them have no idea. Beta blockers (commonly prescribed for blood pressure and heart conditions) reduce sweating and limit blood vessel dilation near the skin. Antipsychotic medications impair both sweating and the brain’s temperature-sensing ability. Tricyclic antidepressants decrease sweating. Some newer antidepressants like SSRIs and SNRIs increase sweating, which sounds helpful but can accelerate dehydration.
Antihistamines with anticholinergic properties, the kind found in many over-the-counter sleep aids and allergy medications like diphenhydramine, reduce sweating and impair thermoregulation. Certain anti-seizure medications do the same. Stimulant medications, including those prescribed for ADHD, reduce sweating, limit skin blood flow, and can impair your perception of how hot you actually are. That last effect is particularly dangerous because you may not realize you’re overheating until it’s too late.
If you take any of these medications, you don’t need to stop them in summer. But you do need to be more cautious: hydrate more aggressively, take more frequent breaks from heat, and pay closer attention to early warning signs.
Food, Spice, and Internal Heat
Your body generates heat when digesting food, a process called the thermic effect of food. Some foods amplify this more than others. Spicy ingredients like chili peppers, ginger, black pepper, and cinnamon contain compounds that actively trigger heat production in your body. Protein-rich meals also generate more metabolic heat during digestion than carbohydrates or fats.
On extremely hot days, lighter meals work in your favor. Foods with high water content, like cucumber, lettuce, and celery, contribute to hydration while producing less metabolic heat. Watermelon is a particularly good choice, offering both water and electrolytes. Eating smaller, more frequent meals rather than large ones reduces the peak heat your body generates during digestion.
Practical Habits for Hot Days
Shift outdoor activity to early morning or evening when possible. The heat index, which combines air temperature with humidity, can feel up to 15°F higher in direct sunlight than in shade. That means a day that reads 95°F on your weather app could feel like 110°F if you’re standing in full sun.
Wear loose, light-colored, breathable clothing. Wet a bandana or towel and drape it around your neck, targeting the major blood vessels close to the surface. Take cool (not ice-cold) showers, which lower your core temperature without triggering the shivering response that would generate more heat. If you’re working outdoors, the OSHA-NIOSH Heat Safety Tool app provides real-time heat index readings and hourly forecasts for your specific location, along with recommendations for when to add water breaks, rest periods, or reschedule work entirely.