Working Safely in Heat and Cold
Recognize heat and cold stress, prevent them and respond when a coworker is affected.
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Your body works hard to hold its core temperature near 98.6°F. When heat or cold overloads that system, you lose judgment and coordination first, and that can cause an injury before the temperature itself does. Heat stroke and hypothermia can both kill. Most cases are preventable, and in both, a coworker who notices early can save a life.
What You Will Be Able to Do
- Name the signs of heat exhaustion, heat stroke, hypothermia and frostbite.
- Plan water, rest, shade and acclimatization for hot work.
- Dress and pace yourself for cold work.
- Give the right first response, and know when to call 911.
Heat: How It Builds
Heat stress comes from more than the temperature on a thermometer. Several things add up:
- Air temperature and humidity. Sweat only cools you when it evaporates, and humid air slows that down. The heat index combines the two. At 90°F with 70% humidity, the heat index is about 105°F.
- Direct sun, hot surfaces and radiant heat from furnaces, ovens, kilns and hot roofs. Indoor jobs can be just as dangerous as outdoor ones.
- Hard physical work, which makes heat inside your body.
- Heavy or protective clothing, which traps heat.
- Your own condition: dehydration, poor sleep, illness, age, some medications, alcohol the night before, and not being used to the heat.
New Workers Are at the Highest Risk
Your body needs time to adapt. OSHA reports that most heat deaths happen in the first days on the job, and nearly three out of four happen during the first week. Acclimatization means building up gradually. The common plan for a new worker is to start with about 20% of normal heat exposure on day one and add no more than 20% each day. Workers who have been away for a week or more, or who have been sick, need to build back up too. A sudden heat wave can catch everyone off guard, because no one has adapted yet.
Preventing Heat Illness
- Water. Drink about 1 cup (8 ounces) of cool water every 15 to 20 minutes during hot work, even if you do not feel thirsty. Thirst lags behind your need. Do not drink more than about 6 cups in an hour, because too much water can also harm you. If you sweat for more than a couple of hours, you also need salt, so eat normal meals, and use a drink with electrolytes if your employer provides one.
- Rest. Take breaks, and take more of them as it gets hotter or the work gets harder. Rest is not lost time. It keeps you working safely through the day.
- Shade. Rest in the shade or in a cool area, not next to the job.
- Schedule. Move the heaviest work to the cooler part of the day where you can.
- Clothing. Wear light-colored, breathable clothes and any cooling gear provided. Keep required PPE on.
- Buddy system. Watch each other. A person with heat illness is often the last to notice, because confusion is one of the symptoms.
Heat Illnesses and What to Do
| Condition | Signs | Response |
|---|---|---|
| Heat rash | Red, itchy bumps in skin folds | Keep the skin cool and dry |
| Heat cramps | Painful muscle spasms | Rest in a cool spot, drink water and take in salt. Get help if they last over an hour |
| Heat exhaustion | Heavy sweating, headache, dizziness, nausea, weakness, thirst, irritability | Move to a cool place, loosen clothing, sip water, cool with wet cloths. Get medical care if there is no quick improvement. Do not leave the person alone |
| Heat stroke | Confusion, slurred speech, fainting, seizures, very high temperature. Skin may be hot and dry, or still soaked with sweat | Call 911. Cool the person at once while you wait |
Heat stroke is a medical emergency. Sweating that suddenly stops is a classic sign, but many workers with heat stroke are still sweating, so do not wait for dry skin. Any confusion or strange behavior in hot conditions is heat stroke until proven otherwise.
Warning: With heat stroke, cooling comes first. Call 911, move the person to shade, and cool them quickly: cold water or an ice bath if you have one, or soak their clothes and fan them, and put ice or cold wet cloths on the neck, armpits and groin. Do not give fluids to anyone who is confused or not fully awake.
Do not send a sick worker to their truck or home alone. People have died that way.
Heat Rules
As of November 2026, there is no final federal OSHA heat standard. OSHA proposed one in 2024, and the rulemaking is still open. OSHA still enforces heat hazards under its General Duty Clause, and has inspection programs aimed at heat. Some states have their own enforceable rules, including California, Colorado, Maryland, Minnesota, Nevada, Oregon and Washington. Requirements and temperature triggers differ, and some apply only to certain industries, so ask what applies at your job.
Cold: How It Builds
Cold stress can happen well above freezing. Wind and wet clothes pull heat from your body fast. The wind chill shows what exposed skin feels. At 0°F with a 15 mph wind, the wind chill is about -19°F, and frostbite can set in on exposed skin in about 30 minutes. Other risk factors include being tired, working in wet conditions, skipping food, poor circulation, and some medications.
Preventing Cold Stress
- Layer your clothes. A base layer that moves sweat away from your skin, an insulating layer, and a wind- and waterproof shell. Avoid cotton next to your skin. It stays wet.
- Open up before you sweat. Sweat soaks your layers and chills you when you slow down.
- Cover your head, hands and feet. Wear a liner under your hard hat if allowed. Keep spare dry socks and gloves.
- Take warm breaks in a heated space. Eat, and drink warm, sweet liquids. Limit alcohol, which speeds heat loss.
- Keep moving but pace yourself so you do not get soaked in sweat.
- Use the buddy system. Check each other's faces for pale or waxy patches.
- Watch the tools and the ground. Bare metal can freeze to skin, cold hands drop things, and ice brings its own fall hazards.
Cold Injuries and What to Do
| Condition | Signs | Response |
|---|---|---|
| Hypothermia, early | Shivering, numb hands, clumsiness, fatigue | Move to a warm place, remove wet clothes, add layers, give warm sweet drinks if awake |
| Hypothermia, severe | Shivering stops, confusion, slurred speech, slow breathing, unconsciousness | Call 911. Warm the core gently with blankets. Handle gently. Give CPR if trained and needed |
| Frostbite | Numb, white, waxy or grayish skin, usually on fingers, toes, ears, nose | Get to warmth, cover loosely, do not rub. Get medical care |
| Trench foot | Wet, cold feet that are swollen, numb and red | Dry the feet, warm gently, keep them elevated, get medical care |
Hypothermia means a body temperature below 95°F. When shivering stops and the person is not getting warmer, it is getting worse, not better.
Warning: Do not rub frostbitten skin, and do not warm it with a direct heat source such as a heater or hot water. Numb skin burns without feeling it. If it may freeze again before care, do not thaw it at all.
Common Mistakes
| Mistake | What it costs | Better habit |
|---|---|---|
| Waiting until you are thirsty | You are already behind | Drink on a schedule |
| Pushing through on the first hot day back | The highest-risk time for heat stroke | Build up gradually |
| Waiting for dry skin to call it heat stroke | Lost minutes | Treat confusion as an emergency |
| Sending someone sick to sit in a truck | They get worse alone | Stay with them |
| Cotton layers in cold weather | Wet, chilled body | Wear wicking layers |
| Rubbing frozen fingers | More tissue damage | Warm gently, get care |
Check Your Understanding
1. It is your first week on a roofing crew, and it is 92°F. A coworker who started the same day says he feels sick and dizzy, and now he is having trouble answering simple questions. What do you do?
Treat it as heat stroke. Call 911, get him into shade, soak his clothes and fan him, and put ice or cold cloths on him. Stay with him.
2. Your crew has been working in 75°F weather, and tomorrow it will reach 95°F with high humidity. What should change?
Add water and rest breaks, move heavy work to the morning, set up shade and watch each other. Nobody is used to this heat, so treat the whole crew as new to it.
3. A worker on an ice-cold job has stopped shivering but is confused and clumsy. Is she warming up?
No. That is a sign of severe hypothermia. Call 911, get her to a warm place, remove wet clothes, and cover her with blankets.
4. Your fingertip has turned white and numb. A coworker tells you to rub it and hold it near the heater. What should you do?
Do not. Rubbing and direct heat can make the injury worse. Go inside, warm it gently, and get medical care.
Key Takeaways
- Heat and cold affect your judgment before they knock you down, so use a buddy system.
- New and returning workers are at the highest risk in heat. Build up over several days.
- Water, rest and shade prevent most heat illness.
- Confusion in the heat is an emergency. Call 911 and cool the person right away.
- In the cold, stay dry, dress in layers, and take warm breaks.
- Shivering that stops, or white waxy skin, needs prompt care.