Spotting the signs of Heat Exhaustion and Heat Stroke: Protecting employees during extreme heat

Dr. Arti Rampaul

Insight

5 minutes

29 July 2026

Heat is an occupational health hazard. Exposure to extreme heat can place strain on the body's ability to regulate temperature (known as heat stress) and increase the risk of heat-related illnesses such as heat exhaustion and heat stroke.

What environmental factors increase the risk of heat stress?

  • Air Temperature and Radiant Temperature
    The temperature most people are familiar with, as shown on weather apps, is the temperature measured in the shade.  However, radiant temperature, which reflects the heat exposure from direct sunlight and heat radiated from surrounding surfaces, can be 10 to 15°C higher than the air temperature and, in some environments, even higher.
  • Humidity
    As the body sweats, cooling occurs as sweat evaporates from the skin.  However, with higher humidity, sweat does not evaporate and stays on the skin, making it difficult for the body to cool down. 
  • Wind
    When air movement is limited, sweat evaporates less efficiently, which can further exacerbate heat stress, particularly in hot and humid conditions. Even a light breeze can help with sweat evaporation.

Who is at increased risk of heat stress?

  • Outdoor and manual workers - Working outdoors for extended periods puts individuals at increased risk during times of increased outdoor temperature and humidity. Manual labour generates additional body heat, further increasing the risk of heat stress.
  • Athletes and physically active individuals - Strenuous physical activity generates additional body heat and increases fluid losses through sweating, placing individuals at greater risk of heat-related illness.
  • Chronic conditions - In an attempt to cool the body, additional strain is placed on the heart and kidneys as the body redirects blood to the skin surface. Individuals with certain chronic conditions such as heart disease, kidney disease, asthma or diabetes can feel the strain of heat stress at a lower threshold compared to healthy individuals.  Certain medications can further exacerbate this, including blood pressure medications, diuretics ("water tablets"), antihistamines and some psychotropic medications.
  • People with limited access to cooling measures - Individuals living or working in crowded conditions, temporary accommodation, or environments without adequate cooling may be at increased risk of heat stress.
  • Age - Those at the extremes of age, including older adults (over 65 years) and infants or young children, are at increased risk of heat stress as their body's temperature regulation mechanisms may be less effective, making it harder to dissipate heat.
  • Pregnancy - Pregnant individuals may be more susceptible to heat stress due to increased demands on the body and a higher risk of dehydration.
  • Individuals not yet acclimatised to the climate - Individuals who are new to a hot climate, recently returned from leave, or starting a new outdoor role may not yet be acclimatised to the heat. Acclimatisation is a gradual physiological adaptation that improves the body's ability to regulate temperature and tolerate heat. This process typically takes 7 to 14 days, making workers in their first days back at work particularly vulnerable to heat-related illness.  Gradually increasing exposure to heat over the first 1 to 2 weeks can help workers acclimatise more safely.

Recognise key differences between Heat Exhaustion and Heat Stroke

 

Heat exhaustion

Heatstroke

Overview

Heat exhaustion occurs as the body loses excess water and salt, usually through sweating. Heat exhaustion and heat stroke are on a spectrum of worsening severity.  Left untreated, heat exhaustion can quickly progress to heat stroke, a dangerous heat-related illness. 

Symptoms

  • Excessive sweating
  • Headache
  • Dizziness
  • Increased thirst
  • Nausea and vomiting
  • Muscle cramps
  • Fatigue and weakness
  • Raised body temperature, typically below 40°C
  • Decreased urine output
  • A very high body temperature – 40°C or more
  • Hot skin, which may be dry or damp. Although absence of sweating is a classic sign, some individuals with heat stroke may continue to sweat.
  • Altered mental state – confusion, agitation or aggression
  • Seizures (fits)
  • Dizziness and fainting (loss of consciousness)
  • Fast breathing and a fast heartbeat
  • Clumsiness or slurred speech

 

What to do if you suspect signs of heat exhaustion in an employee

  • Give them cool water to drink in small, frequent amounts if they are fully alert and able to swallow safely. If available, an oral rehydration solution or isotonic sports drink can help replace the fluids and salts lost through sweating.

  • Remove any extra clothing such as jackets and shoes and socks.

  • Have them wash their head, face and neck with cool water and provide cold compress wrapped in cloth to apply around the neck or under the armpit. 

  • Have them lie down and elevate their legs if practical, particularly if they feel dizzy or faint.

  • Arrange medical evaluation if symptoms are severe, if the individual has underlying health conditions, or if symptoms have not improved within 30 minutes.  Stay with them until they are better or until help arrives.

  • Heat stroke is a medical emergency and can be life-threatening. Call emergency services immediately.
  • Take them out of the hot area to a cool area.
  • Remove extra clothing as well as shoes and socks.
  • Cool them quickly using the following methods: 
  • Applying cold water and wetting the skin
  • Soaking clothes with cool water
  • Placing cold wet cloths on the skin – also on the neck, armpits and groin. 
  • If the person is unconscious or not fully responsive, do not give them anything to eat or drink.
  • Stay with them until medical help arrives.
 

Employer responsibilities during extreme heat

Employers should have a heat illness prevention programme and an emergency response procedure for employees showing signs of heat-related illness, including the following measures:

  • Conduct heat risk assessments.
  • Implement a work-rest-hydration schedule for employees exposed to heat.
  • Ensure shaded or air-conditioned rest areas are available.
  • Encourage regular hydration breaks and provide access to cool drinking water.
  • Train managers and employees to recognise signs of heat exhaustion and heat stroke.
  • Implement a buddy system for employees working outdoors or in high-heat environments.
  • Introduce new employees and returning workers to hot environments gradually to allow for safe acclimatisation.

Any questions?

Howden support our clients with a suite of Lifestyle medicine programs that can be specifically designed to cater for your business. 

If you need more information, or have any questions or comments, please write to us on [email protected]

References:

  1. https://www.who.int/news-room/fact-sheets/detail/climate-change-heat-and-health
  2. Heat-related Illnesses | Heat | CDC
  3. Heat and health - Lancet Countdown
  4. Heat exhaustion and heatstroke - NHS
  5. Heat - Prevention | Occupational Safety and Health Administration
  6. Working on a warmer planet: The effect of heat stress on productivity and decent work | International Labour Organization

Disclaimer: 

The content in this article is for general informational purpose and is not meant to replace or substitute for professional medical advice, diagnosis or treatment.  Always consult a qualified healthcare professional with any questions or concerns about your health.