Weather and thermal stress safety


Hot temperature exposure and safety

What causes heat stress?
What are signs and symptoms?
How to prevent exposures?
What if someone is feeling ill from heat exposure?

Cold temperature exposure and safety (Coming soon!)

Hot temperature exposure and safety

What causes heat stress?

Working in hot environments, outdoors and indoors, can affect the body’s cooling system. If the body is unable to cool itself, heat stress can occur. If not recognized early, this can quickly develop into more serious and life-threatening conditions. Physical exertion and outdoor activities increase this risk if precautions are not taken.

What are signs and symptoms?

As a worker’s body heats up it loses fluids and salt through sweat. As workers dehydrate they are less able to cool themselves down. Workers in a hot environment should be aware of these warning signs of heat stress:

  • Excessive sweating
  • Dizziness
  • Nausea

If heat stress is not recognized and treated early, it can lead to heat disorders, which have serious effects on the body. These include:

Heat cramps Heat Exhaustion Heat stroke
  • Painful muscle cramps
  • Can lead to heat exhaustion if left untreated
  • Shallow breathing
  • Increased heart rate
  • Weak, rapid pulse
  • Cool, pale, clammy skin
  • Sweating
  • Weakness, fatigue, dizziness
  • Headache and nausea
  • Fainting
  • Muscle cramps
  • Can lead to heat stroke if left untreated
  • Hot, dry, flushed skin
  • No longer sweating
  • Agitation and confusion
  • Decreased level of consciousness and awareness
  • Headache
  • Nausea and vomiting
  • Seizures
  • Increase in breathing rate
  • Irregular pulse
  • Shock
  • Cardiac arrest

How to prevent exposures?


  • Heat Stress Awareness (online):  This course helps increase awareness of the risk factors for those potentially exposed to heat, the associated heat stress disorders, and controls/measures to protect against heat stress.


General guidance

  • Monitor heat conditions and require workers not to work alone.
  • Review risk assessments and specific safe work procedures, and adjust as necessary.
  • Communicate and review procedures with workers routinely.
  • Ensure there is adequate first-aid coverage and emergency procedures are in place.
  • Be aware of and check the signs and symptoms for yourself and co-workers.


Review the hierarchy of controls

  • Move tasks to cooler days, times (typically before 11 a.m.) or environments.
  • Change work practices and policies to limit the risk.
  • Make physical modifications to facilities, equipment, processes to reduce exposure.
  • Establish cooling areas with shade and water.
  • Determine worker’s acclimation status.
  • Determine appropriate work-rest cycles; when a worker feels ill it may be too late.
  • Rotate work activities or use additional workers to reduce exposure.
  • Drink plenty of water.
  • Take rest breaks in a cool, well-ventilated area.
  • Wear light-coloured, loose-fitting clothing made of breathable fabric, such as cotton.


Common Outdoor Guidance

  • Protect yourself from the sun by staying in the shade, avoiding direct sun mid-day, wearing a hat and protective clothing, using sunscreen, and wearing UV-protective eyewear.
  • Seek cooler, breezier areas when outdoors, such as large spaces with lots of trees.
  • Stay hydrated by drinking water regularly, even more than you think you need.
  • Take it slow with outdoor activities, rest and relax often if you feel fatigued.


Common Indoor Guidance

  • Make your space as comfortable as possible.
  • Close blinds and shutters during the daytime and open them at night if the space is occupied.  Open windows at night to let in cooler air if the space is occupied. Note: blinds, shutters and windows should always be closed if the space is not occupied to mitigate security risks
  • If you have air conditioning, use it to take the edge off indoor heat.
  • If you don’t have air-conditioning, take shelter in the coolest room in your home and use a fan. Blowing a fan across a pan of ice water can create a cool breeze.
  • Cool showers and misting yourself and your clothing with cool water will help keep you from overheating.
  • Stay hydrated by drinking water regularly, even more than you think you need.
  • Check in regularly with vulnerable people by phone or video.



If you need assistance in determining ongoing heat exposure risks and evaluating the controls in place, please contact the Safety & Risk Services Occupational Hygiene Advisor (604-822-2029).


What if someone is feeling ill from heat exposure?

Signs of progress to heat stroke should be considered a medical emergency where 911 must be called and first aid notified.

Typically for heat disorders other than Heat Stroke, the individual can be moved to a cooler environment and call first aid.

Additional support, resources, and references

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Cold temperature exposure and safety

This information is coming soon