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Extreme Temperatures

Working in extreme temperatures can have devasting impacts on workers' health, safety and well-being.



Just as cold temperatures can adversely affect the body, so can work in hot environments. To keep internal temperatures within safe limits, the body must get rid of excess heat when the air temperature is high and/or the physical workload is very heavy. This is achieved primarily through the varying rate and depth of blood circulation and the evaporation of perspiration from the skin. 

As air temperatures approach normal skin temperature, the body has a harder time cooling itself. Periods of high humidity make the problem worse. Under these conditions, hard physical work becomes more difficult to perform. In turn, work in such an environment may lead to an increase in worker accidents, hyperthermia illnesses and fatalities as well as a decrease in the affected worker's health, efficiency and performance capabilities. 


Exposure to cold temperatures may cause the body's internal temperature to fall below safe limits. This occurs when the body loses heat faster than it can produce it. The body's heat loss will also be affected by factors such as temperature, the amount of moisture in the air (humidity), the amount of wind and the type of PPE that is worn.

As the body loses heat, blood vessels in the skin constrict to conserve internal heat. Thus, in cold environments, a worker's hands and feet are affected first. If the body continues to lose heat, involuntary shivers may occur. Involuntary shivers are both the body's way of attempting to produce heat and the first warning of hypothermia, or decreased body temperature. Additional heat loss may cause the brain to become less efficient, produce speech difficulty, forgetfulness, disorientation, loss of manual dexterity and possibly death.  


Extreme heat-related illnesses include:

  • Heat exhaustion.
  • Heatstroke.
  • Muscle cramps.
  • Heat swelling.
  • Fainting.

For workers worldwide, heatstroke, a condition of hyperthermia is the most serious heat-related illness. Heatstroke is a condition caused by the body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures, leading to the body's core temperature becoming too high. Hyperthermia happens gradually and starts with with heat cramps and then progresses to heat exhaustion and eventually heatstroke if left untreated. 

Workers who work in extremely hot conditions are at the highest risk for experiencing heatstroke due to their exertion levels and prolonged exposure to high temperatures.

Heatstroke requires emergency treatment. Untreated heatstroke can quickly damage the brain, heart, kidneys and muscles. The damage worsens the longer treatment is delayed, increasing the risk of serious complications or death.

Symptoms of heatstroke include:

  • Internal body temperature > 39 C (103 F).
  • Losing consciousness.
  • Reddish skin that feels hot to touch.
  • Strong and fast pulse rate.

Heatstroke can result in a number of complications, depending on how long the body temperature is high. Severe complications include:

  • Vital organ damage - brain and organ swelling possibly resulting in permanent damage.
  • Death - without prompt and adequate treatment, heatstroke can be fatal.


Extreme cold-related illnesses include:

  • Cold-induced hives.
  • Frostbite.
  • Hypothermia.
  • Trench foot (or immersion foot).

For workers worldwide, hypothermia is the most serious cold-related illness. Hypothermia, or low body temperature, happens when the body starts losing body heat faster than the body can produce it. This can happen for a variety of different factors. Being exposed to cold weather for long periods of time, being immersed in cold water for extended periods of time and having wet clothing in cool outdoor temperatures can all trigger hypothermia.

Hypothermia starts with shivering, which indicates the body is trying to produce heat. If the symptoms progress, speech can be affected and seem slurred. Symptoms will continue to progress and a worker may notice a lack of coordination, shallow breathing, low energy and possibly memory loss. The symptoms of hypothermia are often gradual and a worker may not be aware of the situation they are in.    

Hypothermia is something workers have to take special preventative measures against when working outdoors. Not wearing proper layers and working in sweaty base layer clothing can speed up the symptoms of hypothermia.

Symptoms of hypothermia include:

  • Clumsiness or lack of coordination.
  • Confusion or memory loss.
  • Drowsiness or very low energy.
  • Loss of consciousness.
  • Shivering.
  • Slow, shallow breathing.
  • Slurred speech and mumbling.
  • Weak pulse.

If left untreated, hypothermia can lead to various medical conditions, including:

  • Cardiac arrest.
  • Coma.
  • Death.
  • Liver damage.
  • Kidney failure. 


  • Recognise the environmental and workplace conditions that can be dangerous.
  • Learn the signs and symptoms of cold-induced illnesses and injuries and what to do to help workers.
  • Workers should be encouraged to wear proper PPE for cold, wet and windy conditions including layers so they can adjust to changing conditions.
  • Workers should take frequent short breaks in warm dry shelters to allow the body to warm up.
  • Avoid exhaustion or fatigue because energy is needed to keep muscles warm.
  • Use the buddy system - work in pairs so that one worker can recognise the danger signs.