Staying cool while working in the heat comes down to managing two things: how fast your body generates heat and how efficiently it sheds that heat. Your body’s thermoregulation system can handle surprisingly high air temperatures, up to 130°F in dry conditions, but only when you give it the right support. When that system gets overwhelmed and your core temperature climbs past 104°F, you’re in dangerous territory. The good news is that most heat-related problems are preventable with the right hydration, timing, clothing, and awareness.
How Your Body Loses Heat
Your body sheds heat through three main channels: radiation (heat flowing off your skin into cooler air), conduction (direct contact with something cooler), and evaporation (sweat turning to vapor and carrying heat away). When the air temperature is lower than your skin temperature, all three work together. But once the surrounding air is hotter than your skin, radiation and conduction actually start adding heat to your body instead of removing it. At that point, evaporation is the only cooling mechanism you have left.
This is why humidity matters so much. In dry heat, sweat evaporates quickly and cools you effectively. In humid conditions, the air is already saturated with moisture, so your sweat drips off without evaporating, and your cooling system stalls. If you work in direct sunlight, the standard heat index (which assumes shade) underestimates your actual heat exposure. The wet bulb globe temperature, or WBGT, is a better measure because it factors in direct sun, wind speed, and cloud cover. OSHA, the military, and most athletic programs use WBGT to set work-rest guidelines. Many weather apps and portable monitors now report it.
Drink Before You’re Thirsty
OSHA recommends drinking one cup (8 ounces) of water every 15 to 20 minutes while working in the heat. That works out to roughly 32 ounces per hour. Don’t wait until you feel thirsty, because by that point you’re already mildly dehydrated and your body’s cooling efficiency has dropped. There is an upper limit: no more than 48 ounces per hour, since drinking too much water too fast can dilute your blood sodium to dangerous levels.
Plain water is fine for moderate heat exposure, but if you’re sweating heavily for more than an hour, you need to replace electrolytes too. Your sweat contains sodium, potassium, and chloride, and losing too much of these minerals causes cramping, fatigue, and eventually more serious problems. A good oral rehydration drink provides about 20 to 30 milliequivalents of sodium per liter and a small amount of potassium, with some carbohydrate (5 to 10 percent) for energy. Sports drinks approximate this, though many commercial options are heavy on sugar and light on sodium. Diluting a sports drink with equal parts water, or adding a quarter teaspoon of salt to a liter of water, gets you closer to what your body actually needs.
Pre-Cool Before Your Shift
Lowering your core temperature before you start working gives your body a larger buffer before it reaches dangerous levels. Research on workers wearing heavy protective equipment found that drinking about 500 milliliters (roughly 16 ounces) of ice slurry 15 minutes before starting work reduced core temperature by about 0.24°C and kept physiological strain lower for up to 30 minutes into the work period. That may sound like a small number, but in heat stress physiology, a fraction of a degree translates to meaningful extra time before your body hits its limits.
You can make a basic ice slurry by blending ice with water or a sports drink until it reaches a slushy consistency. Forearm and hand immersion in cold water (around 50 to 65°F) for 20 to 30 minutes is another option and can reduce core temperature rise during subsequent work by 0.3 to 0.4°C. If you have access to both, combining cold drink and forearm cooling gives you the best results. The key is timing: do it in the 15 to 30 minutes right before you head into the heat, not an hour beforehand.
What to Wear and Carry
Clothing choices make a real difference. Light-colored, loose-fitting fabrics allow air to circulate over your skin and reflect more solar radiation than dark colors. Moisture-wicking synthetic fabrics pull sweat away from your skin and spread it across a larger surface area, which speeds evaporation. A wide-brimmed hat or hard hat with a neck shade blocks direct sun from your head and neck, where blood vessels run close to the surface.
Cooling vests with phase change material inserts (the kind that solidify when you freeze them, like reusable ice packs) provide active cooling against your torso. Studies on workers in protective equipment found that these vests reduced average skin temperature by about 0.65°C, with the strongest cooling effect on the chest. They typically last one to three hours depending on the ambient temperature and how physically demanding the work is. Having a second set of inserts in a cooler lets you swap them out on breaks. Evaporative cooling vests, which you soak in water, work well in dry climates but lose effectiveness in high humidity for the same reason your sweat does.
Cooling towels around your neck and wrists target areas where blood passes close to the skin surface, helping cool your circulating blood. They’re cheap, easy to re-wet, and surprisingly effective as a supplement to other strategies.
Build Up Your Tolerance Gradually
Your body adapts to heat over time through a process called acclimatization. An acclimatized worker sweats earlier, sweats more, loses fewer electrolytes in that sweat, and maintains a lower heart rate at the same workload compared to someone who hasn’t adapted. The CDC and NIOSH recommend a gradual buildup over 7 to 14 days. If you’re new to a hot work environment, start at no more than 20 percent of a full heat exposure on day one, then increase by no more than 20 percent each day after that.
Workers returning after a week or more away from the heat (vacation, illness, or a stretch of cool weather) lose some of their acclimatization and should ease back in over a few days rather than jumping to full intensity. Monday mornings after a cool weekend are a common time for heat illness, because workers lose a small amount of tolerance even over two days off.
Schedule Work Around the Heat
When you have any control over your schedule, front-load the most physically demanding tasks to the early morning hours when temperatures are lowest. Save lighter duties for the peak heat window, typically between noon and 4 p.m. Take rest breaks in shaded or air-conditioned areas. Even five minutes in the shade with airflow allows your body to dump stored heat before you go back out.
Rotating between outdoor and indoor tasks, when possible, gives your core temperature a chance to drop. The buddy system also matters: heat stress impairs judgment before it causes collapse, so having someone who can notice early warning signs in a coworker is one of the most effective safety measures available.
Recognizing Heat Exhaustion and Heat Stroke
Heat exhaustion is the warning stage. Your core temperature climbs to between 101°F and 104°F, and you may notice heavy sweating, pale skin, muscle cramps, headache, dizziness, weakness, rapid breathing, or nausea. At this point, moving to a cool area, drinking fluids, and resting will usually bring your temperature back down.
Heat stroke is the emergency. Core temperature rises above 104°F, and the body’s cooling system begins to fail. The signs shift noticeably: skin becomes dry and red instead of pale and sweaty, because sweating has stopped. Neurological symptoms appear, including confusion, slurred speech, aggression, hallucinations, stumbling, or seizures. Heat stroke can cause permanent brain damage or death within minutes. If you see these signs in yourself or a coworker, call 911 immediately and begin active cooling (cold water, ice packs to the neck, armpits, and groin) while waiting for help.
The critical distinction is neurological: confusion, personality changes, and loss of coordination mark the shift from exhaustion to stroke. A worker who seems “off,” clumsy, or irritable in the heat should be taken seriously, not brushed off.