FROM THE FIELD: Theo McPherson
July brings peak paving and excavation weather to Manitoba, but it also introduces one of the industry’s toughest hidden challenges: extreme heat. Working long hours under the relentless prairie sun puts heavy construction crews at severe risk of dehydration, heat exhaustion, and heat stroke. Protecting your workforce from extreme temperatures is essential to maintaining productivity and preventing serious medical emergencies this summer.
When workers are exposed to high temperatures, their bodies struggle to cool down. Early signs of heat-related illness include excessive sweating, dizziness, and muscle cramps. If left unchecked, these symptoms can quickly escalate into a life-threatening heat stroke.
To combat this, worksite supervisors must proactively adjust daily operations. Start by scheduling the most physically demanding tasks for the cooler, early morning hours.
Employers should also enforce mandatory breaks in shaded or air-conditioned areas while at the same time, avoiding repeated, rapid temperature swings between extreme heat and cold air conditioning as this can stress your body. The sudden shifts force your cardiovascular system and thermal regulatory systems to work overtime, which can trigger headaches, muscle stiffness, and respiratory irritation, so keep temperature changes within reason. Access to cool, clean drinking water must always be available. Crew leaders need to ensure every worker understands how to recognize the warning signs of heat stress in themselves and their peers.
Humidex seat stress response table
Many Canadian health and safety organizations utilize this recognized guideline to implement work-relief cycles and controls for hot, humid environments.
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Humidex
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Risk Level / Actions Required
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34°C – 37°C
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Warning: Post notice. Ensure workers drink extra water.
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38°C – 39°C
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Action: Provide 15 minutes of relief per hour and 1 cup (240 mL) of water every 20 minutes.
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40°C – 42°C
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Increased Action: Provide 30 minutes of relief per hour in addition to the above water provisions.
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43°C +
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Stop Work: Proceed to emergency heat stress protocol.
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