Heat stress puts workers at serious risk, especially during long shifts in direct sun or confined spaces with limited airflow. Crews wearing heavy gear or pushing through demanding tasks are even more vulnerable. It doesn’t take extreme temperatures to cause problems—just the right conditions, a bit of exertion, and not enough water. This heat stress toolbox talk walks through what heat stress looks like, how it progresses, and what your crew can do to stay safe. You’ll also find tips for planning around high heat, plus reminders acclimatization and OSHA compliance.
Why Heat Awareness Matters on Construction Sites
Construction crews face some of the highest risks for heat illness across all industries. The combination of physical labor, exposure to sun and radiant heat, and the need for heavy PPE creates ideal conditions for heat stress—especially during peak summer months.
And the risk isn’t just theoretical:
- Over one-third of all heat-related workplace deaths happen in construction, according to the CDC.
- According to a study, construction workers are 13x more likely to die from heat-related illnesses.
- Between 50% and 70% of fatalities occur within the first few days of working in hot conditions, often because workers aren’t given time to acclimatize.
- About 75% of heat-related deaths occur during June, July, and August.
- A recent study that analyzed 32 construction workers in Kansas City in July reported that more than 60% of the workers arrived at the jobsite dehydrated.
- Symptoms often go unreported, especially when workers feel pressure to finish a task or tough it out—leading to repeat exposure and increased risk.
Even when it doesn’t escalate into a medical emergency, heat stress impacts jobsite performance:
- Slower reaction times can turn minor mistakes into serious injuries.
- Fatigue and dehydration lead to poor decision-making and reduced focus.
- Lost productivity from unscheduled breaks or early shutdowns adds up fast.
- Increased incident rates drive up insurance premiums and put safety records at risk.
Raising awareness and building heat safety into your daily routine isn’t just good practice—it protects your crew, your schedule, and your margins.
What Is Heat Stress?
Heat stress occurs when the body absorbs more heat than it can release. As the internal temperature and heart rate rise, the body struggles to regulate itself—especially when a worker is wearing PPE, performing strenuous tasks, or unable to take breaks.
Unchecked, heat stress can result in a cascade of serious heat-related illnesses like heat cramps, heat syncope (fainting), heat exhaustion, and heat stroke.
Heat stroke is a medical emergency. Without rapid intervention, it can lead to organ failure or death. That’s why it’s essential to educate every crew member—from apprentices to supervisors—on how to prevent and respond to early symptoms.
What are the Symptoms of Heat Illness?
Spotting the early signs of heat illness can prevent a serious medical emergency. Crews should be trained to watch for symptoms in themselves and their coworkers—especially on high-exertion days or during the first week back in the heat.
The most common early symptoms of heat illness (heat cramps / heat exhaustion) include:
- Heavy, continuous sweating – The body is struggling to cool itself and may be losing fluids faster than they can be replaced.
- Headache, dizziness, or lightheadedness – Especially dangerous if the worker is on a ladder, scaffold, or working near traffic.
- Muscle cramps – Often in the legs or arms, caused by salt loss through sweat.
- Pale or clammy skin – A sign that blood flow is being redirected away from the skin surface.
- Nausea or vomiting – The body’s internal temperature is rising past the point of simple dehydration.
- Unusual fatigue or irritability – Mental and physical performance starts dropping before the worker realizes something’s wrong.
- Feeling faint when standing – May signal low blood pressure due to fluid loss and reduced circulation.
These symptoms should always prompt a pause. Move the worker to shade or a cool area, offer water, and monitor closely. If symptoms don’t improve within 15–20 minutes, escalate care.
Severe symptoms that require immediate medical help (heat stroke) and a call to 911 include:
- Confusion or disorientation – May appear dazed, unable to follow instructions, or acting irrationally.
- Slurred speech or stumbling – Often mistaken for fatigue or dehydration but may indicate severe overheating.
- Hot, dry skin with no sweating – A key indicator that the body has stopped regulating temperature.
- Rapid pulse and shallow breathing – The cardiovascular system is under extreme strain.
- Seizures or convulsions – This is a late-stage sign of heat stroke and requires urgent care.
- Loss of consciousness – The worker may collapse without warning. Begin cooling efforts and monitor breathing while waiting for EMS.
Never tell someone to “tough it out” or “just take five.” Heat illness can escalate fast, especially when early symptoms are ignored. Prioritize response over production—every time.
Treating Heat Stroke
As mentioned in the previous section, heat stroke is a serious health crisis and often requires medical intervention, but there are a few things you can do to treat the symptoms while waiting for help:
- Move the person to a cool location in the shade or indoors.
- Remove or loosen excess or wet clothing.
- Offer water or a sports drink with electrolytes.
- Apply cold, wet cloths or ice packs to the underarms, wrists, and groin.
A couple things to remember:
- Never offer beverages containing alcohol or caffeine.
- Never give fluids to an unconscious person.
What Increases Heat Stress Risk?
Heat stress isn’t caused by temperature alone. It’s the result of multiple factors—environmental conditions, physical workload, and even how well a worker’s body is prepared to handle the heat.
Environmental Factors That Raise Heat Stress Risk:
- High temperatures and humidity reduce the body’s ability to cool through sweat, accelerating the onset of heat stress.
- Lack of airflow or ventilation traps heat around the body, especially in confined or enclosed workspaces.
- Direct sun exposure increases body temperature rapidly, particularly on unshaded or reflective surfaces.
- Hot materials and equipment—like asphalt, metal scaffolding, or newly poured concrete—add radiant heat to the work environment.
- Poorly ventilated interiors can retain heat long after outdoor temperatures drop, creating hidden risks even on milder days.
Physical and Behavioral Risk Heat Stress Factors:
- Heavy physical exertion raises internal body temperature, especially during tasks like lifting, carrying, or jackhammering.
- Wearing PPE or non-breathable gear (e.g. Tyvek suits, respirators, harnesses) traps heat and limits the body’s ability to cool down.
- Lack of acclimatization is a major factor—new hires or workers returning after time off are especially vulnerable.
- Working alone or without oversight makes it harder to spot the early signs of heat stress or get help quickly.
- Dehydration, fatigue, or prior heat exposure can compound risk, even before the day begins.
Construction Jobs That Carry Higher Risk for Heat Stress:
- Crews working on rooftops or open decks during peak sunlight hours.
- Concrete and asphalt teams standing near freshly poured or curing material.
- Demolition or interior crews operating in non-ventilated spaces with no air movement.
- Electricians or HVAC techs working in attics, crawlspaces, or mechanical rooms with poor airflow and no shade.
Recognizing these high-risk scenarios ahead of time helps supervisors adjust schedules, rotate tasks, and set up cooling stations before the crew starts feeling it.
Heat Stress Prevention on the Jobsite
OSHA’s recommended approach to heat illness prevention is simple: Water. Rest. Shade. But there’s more you can do. Need more jobsite-ready strategies? Check out our Beat the Heat post for actionable tips and tricks like these:
1. Provide Adequate Hydration
- Make cool water available within 25 feet of all work areas.
- Encourage drinking 8 oz. every 15–20 minutes, even if workers aren’t thirsty.
- Electrolyte drinks (e.g., Gatorade, drip packs) can help replace salts during prolonged exertion.
2. Schedule Smart
- Start early to avoid the hottest parts of the day (typically 11 AM to 3 PM).
- Rotate workers or use a buddy system for high-exertion tasks.
- Shorten shifts during extreme heat, especially for new hires.
3. Create Cooling Areas
- Provide access to shaded rest areas, misting fans, or air-conditioned trailers where possible.
- Cool-down breaks should be mandatory—not optional—during peak heat.
4. Adjust PPE and Clothing
- Use vented hard hats, light-colored clothing, and breathable materials.
- Avoid heavy, dark fabrics that trap heat.
- Train crews to remove unnecessary layers during rest breaks (when safe to do so).
5. Train and Acclimatize
- Gradually increase workload for new or returning workers over 7–14 days.
- Provide toolbox talks and formal training on heat illness signs, prevention, and response.
- Make sure supervisors know how to activate emergency protocols.
What Is Acclimatization and Why Does It Matter?
Acclimatization is the process of getting the body used to working in hot conditions. It allows workers to gradually build up a tolerance to heat stress by adjusting how their bodies regulate temperature, store fluids, and recover from exertion.
It’s one of the most effective tools in heat illness prevention—and one of the most overlooked. Many serious incidents happen not because the conditions were extreme, but because workers were pushed too hard too soon.
A Simple Acclimatization Schedule
- Days 1–3: Limit new or returning workers to no more than 50% of their typical workload.
- Days 4–7: Increase work duration by 10–20% each day, based on how well the worker is handling the conditions.
- After Day 7: Full work capacity is generally safe, but continue to monitor for signs of fatigue or heat stress—especially during heatwaves.
This process isn’t just for new hires. Anyone returning after a week off, coming from indoor duties, or starting a new task in hotter conditions should follow the same ramp-up approach.
Supervisors should build this into scheduling and staffing plans, and make sure acclimatization is treated as a safety requirement—not a performance issue.
Safety Tips for Working in the Heat
Practical habits make the difference between routine work and a 911 call. Here’s what your crews need to remember:
- Drink water constantly—not just at lunch.
- Avoid caffeine and energy drinks, which dehydrate the body.
- Wear sunglasses and sunscreen to reduce sun strain.
- Use shade creatively—portable tents, rigged tarps, or truck beds.
- Recognize when to speak up. If a coworker looks off, ask. If a break is needed, take it.
- Report symptoms early—heat illness doesn’t fix itself.
Find out ways to ‘beat the heat’ while working construction and how to avoid heat illness so you can stay productive and healthy on site.
Beat the Heat: How to Avoid Heat Illness Working Construction
OSHA Requirements for Heat Safety
While there’s no standalone federal heat standard (yet), that doesn’t mean employers are off the hook. Under OSHA’s General Duty Clause, every employer is required to provide a workplace free from recognized hazards—including excessive heat.
In recent years, OSHA has made heat illness a top enforcement priority, especially on construction sites. In 2024, the agency introduced proposed rules aimed at formalizing what many jobsite safety programs should already include.
What OSHA Expects from Employers
If you’re managing crews in hot conditions, you should already have the following in place:
- A written heat illness prevention program, tailored to your work environment, crews, and seasonality.
- Daily heat hazard assessments, using both temperature and humidity (i.e., the heat index—not just the thermometer reading).
- Worker training on the causes, symptoms, and treatment of heat stress and heat stroke.
- Access to water, shade, and regular rest breaks, especially during peak heat or when workers are wearing heavy PPE.
- Emergency procedures for responding to heat stroke, including who to contact, how to cool a worker down, and how to document the incident.
These expectations aren’t optional. As inspections increase and proposed regulations move forward, now’s the time to formalize your program—or risk costly fines and reputational damage. Read our full breakdown of OSHA’s 2024 heat rules and what they mean for your crew.
On August 30, 2024, OSHA published a Notice of Proposed Rulemaking aimed at protecting workers from heat hazards. Learn more here.
OSHA Heat Rules 2024: Protecting Workers from Heat Hazards
Final Thoughts
Heat stress is serious—and preventable. With the right preparation, education, and tools, your team can stay safe, productive, and compliant, even in the hottest conditions.
✅ Train your crews
✅ Plan your shifts
✅ Monitor your workers
✅ Use technology to reduce the admin burden