A-Z Health Topics | Te hāpori (Ngā kaupapa hauora) Heat and Heatwaves

Heat and Heatwaves

Heat and Heatwaves

Heatwaves are often underestimated, as they are not as visibly hazardous as floods, storms, or tornadoes. However, they present a significant health risk to individuals and communities.

There is no standard definition of a heatwave, however the World Meteorological Organization (2015) defines a heatwave as:

"a marked unusual hot weather (max, min and daily average) over a region persisting at least two consecutive days during the hot period of the year based on local climatological conditions, with thermal conditions recorded above given thresholds."

 

 

Who is most at risk from extreme heat?

Although anyone at any time can suffer from heat-related illness, some people are at greater risk than others. Babies and infants, older people, those with pre-existing medical conditions or on certain medications, and people living alone are more at risk. Pets and livestock are also susceptible.

 

The impact of heat on health and health services

Exposure to hotter than average conditions compromise the body’s ability to regulate temperature and result in rapid rises in the human body gaining heat. Even small differences from seasonal average temperatures are associated with increased illness and death and excessive heat can occur during extreme hot spells in warm and cool countries alike.

The duration of excessive heat plays an important role in how people are affected by a heatwave.

Heat causes a range of heat related conditions and worsens current health issues which increase the number of emergency department admissions and demand for hospital and primary care services. 

 

Heat impacts on health

Heatwaves can have a profound impact on individuals' health, especially for the elderly, infants and children, individuals with chronic health conditions, and those pregnant. Heat can directly cause or worsen existing health issues:

Extreme heat can cause illness and death and can affect anyone at any time. For example; heat rash, cramps, sunburn, Heat stroke/Heat exhaustion.

Temperature extremes can also worsen chronic conditions, including cardiovascular, respiratory, and cerebrovascular disease and diabetes-related conditions. 

The effects of heat may be exacerbated in cities, due to the urban heat island (UHI) effect, the livelihoods and wellbeing of non-urban communities can also be severely disrupted during and after periods of unusually hot weather.

 

Mental health and wellbeing 

Heat not only can affect the physical health of individuals, but it also has effects on mental health. During increased temperatures both during heatwaves and at higher ambient temperatures mental health can worsen with increased mental health related harm, violence and aggression. 

Heatwaves also hinder travel, work, social interactions, and participation in activities, affecting an individual's overall wellbeing. Moreover, heatwaves not only impact humans but also animals, which has both behavioural and economic implications. Pets and livestock are susceptible to heat-related illnesses during heatwaves. Although research on animals and heatwaves is limited, evidence suggests that they share similar risk factors with humans, and therefore preventive measures will be required for pets and agricultural animals too. 

 

 

How to reduce the impact of heat

Prepare your property for high heats. If you have air conditioning, be sure that it is in working order.

If you do not have air conditioning or if there is a power outage, find locations where you can stay cool. For example, a public library, shopping mall, or a public cooling centre. Plan how you will get there.

Create a support team of people you may assist and who can assist you. Check in with them often to make sure that everyone is safe.

 

Get ready before a heatwave

  • Keep up to date with MetService weather forecasts.

  • Prepare your property for high heats. If you have air conditioning, be sure that it is in working order.

    If you do not have air conditioning or if there is a power outage, identify locations where you can stay cool. For example, a public library, shopping mall. 

  • Work out what supplies you might need and make a plan. Have materials to cover windows such as dark curtains or carboard to keep the house cool.
  • Make sure all your animals and livestock have access to shade, preferably natural shade, and a reliable and safe water supply.

 

What to do when a heatwave is forecast

Before a heatwave

  • Prepare you house, pull your curtains or cover your windows to keep your house cool and have windows open to catch the breeze.
  • Bring pets indoors, they are affected by the heat too
  • Do not to leave anyone, particularly children or older people alone in parked cars.
  • Make sure you have a supply of food and water, medications, pet food, baby supplies to last a few days

During a heatwave

  • Stay in an air-conditioned indoor location as much as you can.
  • Keep your home cool by opening windows to catch the breeze and keeping curtains or blinds closed to keep the sun out.
  • Avoid outdoor activities if you can
    • Schedule for early morning or evening when the heat intensity is the lowest
    • Wear loose, lightweight, light-coloured clothing and sunscreen.
    • Pace yourself.
    • If you must go outside, put sun safety practices into action and try to stay out of the sun
  • Check on your support team and friends and family, particularly those that are more vulnerable such as elderly or those living alone.
  • Drink water. Keep you and your pets hydrated. Drink more fluids, regardless of how active you are. Do not wait until you are thirsty to drink.  Check out information on how to stay hydrated.
  • Stay informed during an emergency. Listen to the radio or follow your Civil Defence Emergency Management Group online. Follow the instructions of your local council and civil defence and emergency services.
  • Seek medical help if feeling weak or dizzy or if having intense thirst or a headache - Contact Healthline for advice from trained registered nurses by calling freephone 0800 611 116.

after a heatwave

  • Check for illness or signs of heat sickness and seek help if you or your whanau are unwell.
  • Check on your support team and friends and family, particularly those that are more vulnerable such as elderly or those living alone.
  • Drink water after the hot weather has passed. Keep you and your pets hydrated. Drink more fluids, regardless of how active you are. Do not wait until you are thirsty to drink.
  • Stay alert for extended hot periods and persisting elevated temperatures.

 

Further information

Climate changes and heat

Climate change intensifies and increases the frequency of extreme weather events, a trend that will worsen in the future.

The prevalence of heatwaves is rising globally, with increased frequency, duration, and intensity observed since 1950. Heatwaves will worsen over the coming years, their severity will depend on our future emissions and adaption. 

 

Environmental damage of heatwaves on human health 

Heatwaves have significant environmental impacts, both immediately and in the long term, with consequent effects on human health. Here are examples:

  • Wildfires: Heatwaves raise the risk of wildfires, especially in dry areas with flammable materials. Extreme heat and dry conditions accelerate the rapid spread of fires, causing extensive damage to forests and ecosystems. Wildfires directly impact human health through burns and smoke inhalation injuries, affecting large surrounding populations.
  • Droughts: Heatwaves can trigger droughts by accelerating moisture evaporation from soil and vegetation. This leads to water shortages, crop damage, and ecosystem composition changes. These ripple effects can result in poor health outcomes due to the loss of safe food and water.
  • Oceanic heatwaves and ecosystem changes: Heatwaves in the ocean can cause significant harm to marine ecosystems, including coral bleaching and reef deterioration. They also induce substantial ecosystem changes, particularly in areas where plant and animal tolerance limits are already stretched. These changes will have long-term impacts on New Zealand's farming and fishing industries, disrupting jobs and food production.
  • Infrastructure damage: Heatwaves can harm infrastructure like roads, bridges, and buildings. Extreme heat causes materials such as concrete and asphalt to expand and crack, posing safety hazards and requiring costly repairs. Increased energy demand for air conditioning during heatwaves strains electrical grids and contributes to blackouts. This infrastructure loss can be life-threatening, hindering the effectiveness of air conditioning, a crucial preventive measure during heatwaves, and impeding first responders' access to those in need.

 

Reducing the impacts of heat on human health

Preventing heatwaves is crucial for safeguarding human health.

Higher concentrations of vulnerable populations live in areas prone to hot days, particularly Māori, young children and people living in higher levels of deprivation.  The key to reducing the impact of heatwaves and other extreme climate events is to slow down the rate of climate change.

Solutions to reduce the impact of heatwaves and other environmental impacts of climate change need to be designed to reduce existing disparities and promote equity. 

Infographic - Health Impacts of Climate Change; Heatwaves

 

Mitigation planning for heat

Health New Zealand recommends that Heat Health Plans be developed by emergency services, local government agencies and critical infrastructure providers on how their organisations will respond together and reduce the incidence of heat related illness.

In 2018 Ministry of Health (now Health New Zealand) released a Heat Health Plan Guidelines and Information to support health and community service providers, the health sector, local government and other community organisations prepare their own heat health response plans.

Reducing the impacts of extreme heat does not rest with emergency service providers alone.  This is because measures to counter the effects of heat include:

  • planting trees as shade structures and for their cooling effect;
  • providing drinking-water fountains in public spaces;
  • including water-features in public spaces; and using natural materials for construction (such as wood).
  • identifying populations within the community at greatest risk during heatwaves to allow for targeted planning, improved support and preventative measures.

The key to reducing the impact of heatwaves and other extreme climate events is to slow down the rate of climate change. This requires cutting greenhouse gas emissions.  

For more information

Updated 03 Dec, 2024