Summer heat is no longer something workplaces can treat as a short seasonal inconvenience.
Across Ontario, workers are facing hotter days, longer stretches of extreme heat and rising harm to health from work that is already physically demanding. In Toronto alone, there were 29 heat warning days in summer 2025. And while the hottest days of the year may still be ahead, prevention planning can’t and shouldn’t wait until temperatures are already dangerous.
Heat stress is a workplace hazard. Like other hazards, it must be identified, assessed and controlled.
Book in-person Heat and Cold stress training before Aug. 31st and save 50%
Outdoor and indoor workers can both be affected
Outdoor workers are among those most exposed to extreme heat, especially in construction, road work, landscaping, farming and other physically demanding jobs. But heat stress isn’t limited to outdoor work.
Dangerous heat can also build indoors where workers are exposed to ovens, hot equipment, steam, poor ventilation, heavy protective clothing or strenuous work. The harder the work, the more heat the body generates. When workplace conditions prevent the body from cooling itself, heat stress can quickly become a medical emergency.
Heat-related illness can include heat rash, fainting, heat cramps, heat exhaustion and heat stroke. Heat stroke is the most serious and can cause permanent damage or death if not treated immediately. Heat can also create serious safety hazards when workers experience dizziness, reduced alertness, sweaty palms, fogged safety glasses or physical fatigue. Over time, when heat accumulates in the body, it can damage cells in the brain, heart, kidneys, liver, and muscles. Evidence suggests workers with long-term exposure to heat stress on the job may be more prone to developing chronic kidney disease.
Make work safe
These hazards and their effects are preventable. Prevention starts with the workplace (not the worker).
Too often, heat stress messaging focuses only on telling workers to drink water or “take it easy.” While access to cool drinking water and rest breaks are essential, they aren’t a substitute for proper response and controls. Employers must take every precaution reasonable to protect workers.
Effective heat stress prevention should include formal heat stress monitoring, and a proper response and control plan developed with the joint health and safety committee or health and safety representative. Among other things, this plan should consider temperature and relative humidity (or humidex also adjusted for clothing and radiant heat), appropriate responses to humidex levels, plus a full range of controls, including:
- Reducing heat through cooling systems, insulation, ventilation, equipment maintenance and changes to hot processes
- Installing exhaust systems, shade, barriers, and dehumidifiers
- Redesigning work to reduce physical demands, slow the pace of work, assign additional workers or postpone non-essential tasks during extreme heat
- Scheduling heavy work during cooler parts of the day
- Providing frequent breaks in cool, shaded or air-conditioned areas
- Ensuring workers have access to cool drinking water
- Training workers, their representatives, and supervisors to recognize symptoms and respond quickly
- Using a buddy system to identify early warning signs of heat-related illness
- Creating emergency procedures before a crisis happens.
Sign up for in-person Heat and Cold Stress training before Aug. 31st and pay half the price
Register for Heat and Cold Stress training
Ontario still doesn’t have a specific heat stress regulation under the
Occupational Health and Safety Act. This makes strong workplace policies, training, worker participation and prevention planning even more important.
WHSC’s
Heat and Cold Stress training gives workplace parties the tools to better understand and address the dangers of temperature extremes. Participants explore how the body reacts to temperature extremes, where workers may be exposed to dangerous heat or cold, and how to identify and assess potential health harms and finally, build workplace prevention plans. The course also looks closely at methods for controlling exposure.
In-person training is available for 50% off for a limited time. Register before August 31st to save.
Upcoming in-person classes include:
- Hamilton on July 9 from 1:00 pm to 4:00 pm
- London on July 9 from 12:30 pm to 3:30 pm
- Markham on July 16 from 1:00 pm to 4:00 pm
- Sudbury on July 23 from 12:30 pm to 3:30 pm.
Virtual classes are available at regular prices July 21 from 1:00 pm to 4:00 pm, and December 18 from 9:00 am to 12:00 pm. With demand more classes can be offered.
Heat stress season is starting earlier. Workplaces need to be ready earlier too.
Register for WHSC Heat and Cold Stress training today:
https://www.whsc.on.ca/Training/Training-Registration
Learn more about the dangers of heat stress
Need more information?
Contact a
WHSC Training Services Representative in your area.
Email:
contactus@whsc.on.ca
Visit:
whsc.on.ca
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