Health impacts of heatwaves

• Dehydration occurs when your body does not have enough fluids to keep it working properly. 
• When it is very hot, you may be at increased risk of dehydration.

Signs and symptoms

Signs of dehydration include being thirsty, a dry mouth and dark urine.

Symptoms of mild to moderate dehydration include:

• being thirsty
• dry mouth, including lips and tongue
• light headedness and/or dizziness, particularly when standing up
• headache
• dark urine
• not as much urine as normal. 

Symptoms of extreme dehydration include:

• extreme thirst
• a very dry mouth, including lips and tongue
• fast heart rate  
• fast breathing
• low blood pressure
• fever
• little to no urine
• feeling irritable, drowsy or confused

Treatment

If you suspect a person is dehydrated, encourage them to:

• rest in a cool, well-ventilated area
• remove excess clothing
• drink small amounts of cool water, often 

Prevention

Information on how to prevent dehydration can be found on the Prepare for a heatwave page.

• Heat stress occurs when your body cannot cool itself enough to maintain a healthy temperature (37 °C).
• When it is very hot, you may be at increased risk of heat stress.
• Some people are more at risk of heat stress, including babies and young children, the elderly, and people with some health conditions or on certain medications.

Signs and symptoms

Signs of heat stress include pale skin, excess sweating or no sweating and dark urine.

Symptoms of heat stress include:

• tiredness and lethargy
• headache
• dizziness
• feeling faint
• muscle cramps
• feeling thirsty
• urinating less often.

Treatment

If you suspect a person has heat stress, encourage them to:

• rest in a cool, well-ventilated area
• remove excess clothing
• drink plenty of water
• apply a wet cloth, cold water or ice packs to the skin (armpits and groin).

In conditions likely to cause heat-related health effects always suspect heat stroke if a person becomes acutely unwell or collapses, especially if they don’t recover promptly on lying flat with the legs elevated. Although there are many possible causes of acute illness or collapse, heat stroke is one of the most important.

Prevention

Information on how to prevent heat stress can be found on the Prepare for a heatwave page.

Heat stroke is an uncommon but life threatening complication of grossly elevated body temperature with exercise in heat stressed settings.

REMEMBER: it is early recognition and first aid in heat stroke that is critical to save a life.

The risk is highest with:

• high temperatures and/or
• high humidity and/or
• vigorous activity.

Signs and symptoms

The first signs of heat stroke show in the function of the brain and nervous system. Look for any signs of:

• confusion
• incoherent speech
• abnormal walking
• coma or seizures.

In conditions likely to cause heat-related health effects always suspect heat stroke if a person becomes acutely unwell or collapses, especially if they don’t recover promptly on lying flat with the legs elevated. Although there are many possible causes of acute illness or collapse, heat stroke is one of the most important.

Treatment

Heatstroke is an extreme medical emergency. If not treated immediately, it can lead to permanent damage to vital organs, or even death. Dial triple zero (000) to call an ambulance and stay with the person until the ambulance arrives.

While waiting for the ambulance to arrive:

• STRIP the person of as much clothing as possible
• SOAK with any available water
• FAN vigorously by whatever means possible – improvise, e.g. use a clipboard, bin lid.

When available cool or ice water immersion is the most effective cooling means possible:

• IMMERSE the person up to the neck in a cool or ice bath
• OR
• COVER all of the body with ice water soaked towels that are changed frequently as an alternative if a bath isn’t available but ice is
• REMEMBER: it is early recognition and first aid in heat stroke that is critical to save a life.

Prevention

Information on how to prevent heat stroke can be found on the Prepare for a heatwave page.