Scorching heat doesn’t just make you sweat—it can kill. Every year, thousands of workers are treated for debilitating heat illnesses, with the CDC reporting nearly 800 heat-related worker deaths annually. One-third of those fatalities happen in construction, a stark reminder of how dangerous the workplace can become as temperatures rise. As temperatures soar and heat waves become more frequent, knowing how to recognize and prevent heat illnesses is critical for safety and productivity.
This heat stress training guide dives deep into heat illness symptoms, prevention strategies, and actionable tips to stay safe during extreme heat. From understanding the early warning signs of heat illness to implementing proven OSHA-recommended strategies, get ready for heat safety tips on how to work in the heat, safeguard your workforce and prevent heat stress before it becomes a serious problem.
What is Heat Illness?
According to the NIOSH, in 2023 alone, at least 2325 people died from heat-related causes, with the number potentially being much higher due to heat illnesses often being unreported. Since we’re going to be using the term a lot, let’s first define it.
Heat illness, or hyperthermia, is an umbrella term that encompasses a varied spectrum of disorders caused by exposure to extreme heat, inadequate hydration, and high temperatures. It usually happens when a body struggles to cool itself effectively under extreme heat or physical activity.
The body normally cools itself by sweating, but extreme heat, dehydration, or prolonged exertion can overwhelm this system, leading to dangerous overheating. Heat illnesses can range from mild conditions like a heat rash to severe and life-threatening disorders like heat exhaustion and heatstroke.
Think of heat illness like your phone overheating on a hot day. You’re using it to stream videos, run apps, and maybe it’s sitting in direct sunlight. Eventually, your phone shuts down to protect itself. Your body does the same thing when it’s too hot—except instead of a warning screen, you might feel dizzy, sweaty, or even pass out.
What are the types and symptoms of heat illness?
Recognizing the early signs of heat illness is the key to heat stress prevention in the workplace. There are 4 main types of heat illnesses. Here’s what you need to know about each of them:
Early Signs (Heat Rash):
What it is: A skin irritation caused by blocked sweat glands during excessive sweating.
Cause: Blocked sweat glands during excessive sweating.
Symptoms: Red clusters of small blisters or pimples, typically appearing on the neck, chest, or upper body.
Treatment: Keep the skin cool and dry. Wear loose, breathable clothing and avoid excessive sweating.
Early Warning Signs (Heat Cramps):
What it is: Painful muscle spasms in the legs, arms, or abdomen.
Cause: Dehydration and loss of electrolytes through sweating.
Symptoms: Sudden, sharp cramps in the legs, arms, or abdomen.
Treatment: Drink lots of electrolyte-rich fluids and rest.
Moderate Symptoms (Heat Exhaustion):
What it is: A more severe response to prolonged heat exposure and dehydration.
Cause: Prolonged exposure to heat and loss of bodily fluids through excessive sweating.
Symptoms:
Heavy sweating
Pale or clammy skin
Nausea
Dizziness
Headache
Dark urine
Weak but rapid pulse
Drop in blood pressure
Treatment: Move to a cool, shaded area, rehydrate, loosen clothing, and apply cool compresses to the skin.
Moderate Symptoms (Heat Collapse or Heat Syncope):
What it is: Sudden loss of consciousness due to decreased blood flow to the brain.
Cause: Blood pooling in the legs due to standing in the heat for long periods, dehydration.
Symptoms:
Sudden dizziness or lightheadedness
Brief fainting episodes
Weakness
Sweaty, pale, or clammy skin
Heat Illness Treatment: Rehydrate and use fans, wet towels, or ice packs while lying the individual in a cool, shaded area with their legs elevated.
Severe Symptoms (Heatstroke):
What it is: A life-threatening condition where the body’s heat regulation fails. This is a medical emergency.
Causes: Failure of the body’s heat-regulating mechanisms.
Symptoms:
High body temperature (above 104°F)
Dry, or flushed skin
Confusion, slurred speech, or agitation
Rapid pulse
Loss of consciousness
Heat Illness Treatment: Call 911 immediately. Cool the individual using ice packs, wet towels, or immersion in cool water until emergency services arrive.
By spotting these signs early, you can hydrate, rest, and cool down before the situation gets serious.
Think of heat illness like your phone overheating on a hot day. You’re using it to stream videos, run apps, and maybe it’s sitting in direct sunlight. Eventually, your phone shuts down to protect itself. Your body does the same thing when it’s too hot—except instead of a warning screen, you might feel dizzy, sweaty, or even pass out.
What are the major heat illness risk factors?
Heat illness happens when the body overheats, and certain external and internal risk factors increase the likelihood of heat-related disorders:
Internal risk factors:
Physical exertion: Intense physical activity in hot environments.
Dehydration: Lack of adequate fluids impairs the body’s cooling mechanisms.
Clothing: Heavy or non-breathable clothing traps heat.
Pre-existing medical conditions: Pre-existing illnesses like cardiovascular or respiratory diseases.
Medications: Some drugs can interfere with the body’s ability to regulate heat. Antihistamines, for instance, can reduce sweating, while diuretics can cause dehydration.
Age: Children and older adults (over 65+) are more vulnerable to heat stress.
Weight: Overweight or out of shape individuals are more susceptible to heat illness.
External and environmental heat illness risk factors include:
High temperatures above 85°F
High humidity
Sunlight exposure or thermal heat
Unrestricted work in the heat
How to measure heat stress?
Monitoring heat stress is essential for keeping workers safe in hot environments, and it starts with understanding two key metrics: Heat Index and Wet Bulb Globe Temperature (WBGT).
Heat Index
The heat index combines temperature and relative humidity to determine how hot it feels. When humidity is high, sweat evaporates more slowly, reducing the body’s ability to cool itself, which increases the perceived temperature.
For instance, an 88°F day with 70% humidity can feel like a sweltering 100°F. This index is a quick way to assess heat stress risk, but it’s less accurate while assessing the impact of outdoor physical activity on the body.
The WBGT takes heat measurement to the next level by including multiple factors:
Ambient temperature: The air temperature in the environment.
Humidity: The amount of moisture in the air.
Radiant heat: The heat from the sun or other sources, like equipment.
Air movement: How wind helps or hinders cooling.
The WBGT is widely regarded as the gold standard for workplace safety, providing a comprehensive heat stress evaluation, especially in industries like construction and athletics.
Perry Weather simplifies the process with automated tracking, monitoring, and recording of both the heat index and WBGT, along with other critical heat and weather metrics.
WBGT, where used wisely, far outperforms Heat index in accuracy, but where do we use it? The great outdoors! WBGT is used best outside of any building, athletic center, or any area that is climate controlled.
The U.S Department of Labor’s Occupational Safety and Health Administration (OSHA) has announced the first-ever federal heat safety regulations to protect workers from the threat of extreme heat. These rules are a major step towards mitigating heat-related health risks and, if enforced, would be the first federal heat safety regulations to ensure that workers are better protected against the dangers of rising temperatures and heat illness.
Heat acclimatization is the body’s ability to gradually adapt to hot environments over time. When you’re exposed to heat for several days, your body undergoes physiological changes that help it manage heat stress better.
The process usually takes 1-2 weeks of regular heat exposure and often includes sweating more efficiently, improving blood flow to the skin, and properly regulating the internal body temperature.
Think of a lifeguard starting their summer job. On day one, they’re sweating buckets and feeling lightheaded after a few hours in the sun. By week two, they’re chilling in the chair, barely noticing the heat, even during peak hours. That’s heat acclimatization in action!
Acclimatization Zones
Since the United States is so massive geographically, many regions have their own varying degrees of heat intensity. These regions are categorized into different zones.
Workers in warmer zones tend to acclimatize faster than those in cooler zones, so those new to hot environments will need time to build heat tolerance.
How to Safely Acclimatize Workers
The best way to acclimatize to the heat is to increase the workload performed in a hot setting gradually over a period of 1–2 weeks:
Gradual Acclimatization: To adapt to heat, workers should gradually increase their workload over 1-2 weeks.
Supervisor Awareness: Supervisors should be aware of the risks for unacclimatized workers.
Worker Monitoring: Supervisors should monitor workers during strenuous activities, especially those who are new to hot environments.
Heat Illness Prevention Strategies
Heat illness is preventable with the right precautions and education. By understanding heat illness symptoms, risk factors, and prevention strategies, you can protect yourself and others during extreme heat. First, let’s understand the major heat risk triggers:
Heat Risk Triggers Activities like roofing, construction, or landscaping in direct sunlight can escalate heat exposure. Understanding heat risk triggers—the factors that amplify heat exposure—is essential to creating safer work environments and protecting workers.Here are the key heat risk triggers:
Work conditions: Some limitations on work activities
Employees: Drink 4 cups of water per hour
Observe coworkers for signs of heat illness
For Supervisors:
Ensure shaded, or air-conditioned areas are close to the worksite for breaks
Increase the frequency of hydration and cool-down breaks
Closely monitor and acclimate new or returning employees
High Risk Heat Triggers:
Work conditions: Significant limitations on work activities; consider indoor
work when possible
Employees: Drink 4 cups of cool water per hour
For Supervisors:
Implement 50:10 minute work/rest cycles
Set up a buddy system for monitoring
Ensure employees are properly acclimated to the weather
Closely supervise new employees for at least 7 days
Use thermometers during rest periods to monitor for heat illness
Extreme Risk Heat Triggers:
Work Conditions: Work is limited to critical tasks only
Employees: Drink 4-6 cups of water per hour
For Supervisors:
Assess the nature of work carefully
Provide personal cooling measures (e.g., cooling vests or towels)
Set up shade canopies over work areas and shade areas for rest breaks
Whenever possible, relocate tasks to shaded areas during peak heat hours
Ensure a buddy system is in place and do not leave employees unattended
Use thermometers to monitor employees during breaks
Work Rest Cycles
Proper scheduling helps prevent heat-related illnesses and enhances overall productivity. Employers must implement well-planned work rest cycles. Here’s a breakdown of the key practices employers should follow, along with recommendations for different temperature thresholds:
Shaded Areas for Rest: The employer must maintain shaded areas that accommodate 25% of the workforce at any time. These areas should be open to air or ventilated, allowing employees to sit comfortably without physical contact.
95° F: Regular rest periods for cooling down should be enforced when temperatures exceed 95°F.
103°F (High Risk): A 45-minute work/15-minute rest cycle is recommended at this heat index level.
115°F (Extreme Risk): A 20-minute work/40-minute rest cycle is recommended. Shade or cooling areas must be readily available during these periods.
What to Do During Extreme Heat
Hydrate Frequently: The average person needs to drink at least 3/4th of a gallon of water a day. Drink water every 15-20 minutes, even if you’re not thirsty.
Monitor Weather Conditions: Use apps or systems like Perry Weather to track heat indices.
Wear Appropriate Clothing: Opt for lightweight, light-colored, and breathable fabrics.
Limit Outdoor Activities: Avoid heavy exertion during peak heat hours (10 AM to 4 PM).
Check on Vulnerable Individuals: Ensure children, elderly, and pets are safe and hydrated.
Acclimate Gradually: Allow the body time to adjust to hot environments.
Use Protective Gear: Equip workers with cooling vests or hats.
Provide Education: Train employees on recognizing and responding to heat illness symptoms.
Create a Heat Response Plan: Outline steps for managing heat risks and emergencies.
Use tools like Perry Weather’s heat stress monitoring platform to stay informed and safe. Prioritize hydration, regular breaks, and a proactive heat response plan to mitigate risks and ensure a safe environment for everyone.
Hydration Strategies for Workers
Staying hydrated is one of the most effective (and simple!) ways to prevent heat-related illnesses. Here are practical strategies to ensure workers stay hydrated on the job:
Have Cool Water Readily Available
Provide access to potable water kept at a cool temperature (50–60°F).
Supply at least 1 quart per employee per hour to meet hydration needs. This ensures workers have enough water to drink frequently throughout their shifts.
Establish a Reliable Water Supply Plan
Set up a system for the regular delivery of water and ice to job sites, especially in remote or high-heat areas.
Create backup plans for unforeseen circumstances, such as equipment failures or unexpected spikes in water demand.
Encourage Frequent Hydration
Supervisors should take an active role in reminding employees to drink water regularly—even before they feel thirsty.
In hot weather, the body can lose fluids quickly, and thirst alone is not always a reliable indicator of dehydration.
By implementing these hydration strategies, employers not only safeguard workers’ health but also promote productivity and morale during hot weather conditions. A well-hydrated workforce is a safer, more efficient workforce!
Responsibilities of a Supervisor
Supervisors play a pivotal role in protecting employees from heat-related illnesses, particularly during warmer months. Their responsibilities go beyond basic oversight, encompassing preparation, education, monitoring, and response to ensure worker safety.
Supervisors must train workers before outdoor work begins on recognizing signs and symptoms of heat stress, implementing the heat illness prevention plan, and providing first aid:
Preparing for Outdoor Work
Evaluate Work Conditions: Assess environmental risks like high temperatures, humidity, and PPE requirements before assigning outdoor tasks.
Preemptive Training: Train employees on heat illness prevention and response measures before outdoor work in the heat begins.
Training and Leadership
Supervisor Training: Supervisors should be trained to identify signs of heat stress, implement Heat Illness Prevention Plans (HIPP), and administer first aid.
Worker Education: Educate employees about heat stress risks, hydration techniques, and staying cool.
Preventive Measures
Set Clear Heat Safety Policies: Establish guidelines for safe working conditions in hot weather.
Hydration and Rest:
Ensure unrestricted access to cool, potable water and encourage regular water breaks.
Implement work/rest schedules, especially in extreme heat. Rest breaks must be mandatory and monitored. Don’t let employees skip breaks!
Monitoring Conditions:
Use tools like Perry Weather to track the heat index, assess workplace safety, and adjust work schedules as needed.
Pay close attention to workers wearing heavy, non-breathable PPE or coveralls.
Emergency Response and Acclimatization
Immediate Action: Stay vigilant for signs of heat-related illnesses, such as dizziness, heavy sweating, or confusion, and act swiftly if symptoms arise.
Acclimatization: Gradually increase exposure for new or returning workers, especially those performing strenuous tasks.
Encourage workers to report concerns or symptoms related to heat stress without hesitation.
Conduct a Heat Illness Prevention Stand-down, where policies, training, and safety practices are revisited and reinforced.
By taking proactive measures, supervisors can create a safer, more productive work environment even in the hottest conditions.
With Perry Weather, you can make informed decisions about work-rest cycles, hydration needs, and safety measures, ensuring your team stays cool and productive—even when the temperatures climb.
Don’t leave your team’s safety to chance—try Perry Weather to stay ahead of heat stress and keep your workplace protected and efficient.
