- July 24, 2025
- Kevin Kholer
Working in Hot Temperatures
Heat Can Be Deadly – Even in Canada
Extreme heat isn’t just a concern for tropical climates. Here in Canada, hot temperatures can and do claim lives. Health Canada reports that Toronto saw an average of 120 heat-related deaths annually between 1954 and 2000. In Montreal, at least 50 people died during a single heat wave in July 2018.
For workers, the risk is even higher. Whether it’s due to physical exertion, environmental conditions, or heavy protective gear, many job sites put people at increased risk of heat-related illness and injury.
Understanding Heat Stress
It’s not just the temperature that matters — humidity, radiant heat, air movement, and workload all play a role. When the body can’t cool itself effectively, core temperatures rise and health risks increase.
Here are the key factors that affect the body’s ability to stay cool:
- Air Temperature
- Humidity – high humidity slows sweat evaporation
- Radiant Heat – from the sun or industrial processes
- Air Movement – moving air helps with evaporation
- Clothing – some PPE traps heat, increasing stress
- Physical Activity – the more intense the work, the more heat the body generates
- Individual Differences – age, fitness level, hydration, and medications can also impact tolerance
Workers who are new to hot environments (unacclimated) are at even higher risk.
Types of Heat Illnesses
- Heat illnesses can progress in the following manner:
- Heat stress: Results in a reduced ability to do physical or mental work, the body requires rest to recover from heat exposure.
- Heat exhaustion: Where the body’s dissolved salts balance is upset from excessive sweating without replacing both salt and water. Symptoms can include weakness, intense thirst, nausea, diarrhoea, breathlessness, and numb hands and feet. Recovery usually occurs after resting in a cool area and drinking electrolyte replacing drinks.
- Heat stroke: A more serious condition that can include the following symptoms:
- Dry, hot skin;
- Core temperatures that often exceed 41°C; and
- Complete or partial loss of consciousness.
Heat stroke requires prompt medical help and can lead to death.
Preventing Heat-Related Illnesses
The good news? Heat illnesses are preventable with the right controls:
- Lower ambient temperature or humidity where possible
- Use shade, ventilation, or fans to reduce radiant heat and promote airflow
- Schedule rest breaks in cooler areas
- Reduce physical exertion during peak heat
- Provide access to water and electrolyte drinks
- Use breathable, heat-appropriate PPE
- Allow workers time to acclimatize to hot conditions
The ACGIH (American Conference of Governmental Industrial Hygienists) offers useful guidelines for managing heat in the workplace.
Best Practices for Employers and Teams
- Train workers and supervisors to recognize the early signs of heat stress
- Include heat exposure in your regular hazard assessments
- Establish response plans to support workers showing symptoms
Encourage a culture where people look out for one another in the heat
Working in hot temperatures isn’t just uncomfortable — it can be dangerous. Recognizing the risks and taking proactive steps keeps everyone safer on the job.