Disasters explained: heatwaves

Everything you need to know about heatwaves

Heatwaves and intense hot weather can be extremely dangerous for people.

In fact, it’s one of the most dangerous types of weather-related hazards, with 166,000 people dying from extreme hot weather between 1997-2017. It can cause dehydration, blood clots and induce heatstroke.

Here, you can read and learn more about what they are, why they happen and what their link is to climate change.

Although we have never needed to respond to a heatwave, ShelterBox provides emergency shelter following different types of disasters. This includes droughts, tropical storms and other climate related disasters.

What is a heatwave and why does it happen?

Does climate change cause heatwaves?

What are the effects of heatwaves?

How can I protect myself during a heatwave?

What is a heatwave and why does it happen?

A heatwave is a period of unusually hot weather, often lasting several days. 

According to the Met Office, a heatwave is an extended period of hot weather relative to the expected conditions of the area at that time of year. The effects are more severe when accompanied by high humidity.


Heatwaves usually occur in the summer when we are more likely to see high pressure weather systems. High-pressure systems force air downward, trapping warm ground air in place. This force prevents air from rising and as a result there is nothing to prevent the hot air from getting hotter.

High pressure systems are slow moving and can persist for a prolonged period of time, such as days or weeks.

Does climate change cause heatwaves?

Heatwaves are extreme weather events. Scientists believe that climate change is making heatwaves more severe and more frequent.

A higher concentration of carbon dioxide (CO2) in the atmosphere is making heatwaves more common now than before the industrial revolution. When CO2 builds up in the atmosphere, it traps in heat like a blanket, causing the Earth’s temperature to rise.

As greenhouse gas emissions continue to increase, heatwaves are expected to occur more often and at higher intensity.

thermometer showing high temperature during a heatwave
In England, there are about 2000 heat-related deaths every year (source: NHS).

What are the effects of heatwaves?

As greenhouse gas emissions continue to increase, scientists warn that heatwaves will occur more frequently.

Heatwaves kill thousands of people each year, while more suffer serious health impacts that can linger long after it has passed.

In fact, extreme heat kills more people in the U.S. each year than any other kind of natural hazard (source: National Geographic). In England, the NHS records an average of 2000 heat-related deaths every year.

Vulnerable groups such as very young children, the elderly and people with existing health issues are more likely to experience the impacts of extreme heat because they find it harder to maintain their core body temperature.

Moreover, heatwaves can put a strain on health and emergency services. People are more likely to use more water and energy to run electric cooling systems such as air conditioning units or fans. This increases strain on water, energy and transportation that can cause power shortages or even blackouts. Extreme heat can also affect food security and livelihoods, with crops and livestock being compromised.

How can I protect myself during a heatwave?

There are several simple things you can do to protect yourself during a heatwave.

  • Drink lots of water and fluids, avoiding alcohol as it can cause further dehydration.
  • Avoid exercising during the hottest hours of the day.
  • Stay cool indoors. If you must go outside, stay in the shade and take water with you.
  • Make sure to check on your loved ones who might be vulnerable during a heatwave, like elderly relatives or very young babies.
  • If you have pets, make sure they drink lots of water and keep cool, under shade.

Follow advice from health authorities such as the NHS for more tips on how to cope during a heatwave.

Sources and references: Met Office, WHO, National Geographic, New York Times, BBC, NHS.

Explore more

Disasters explained: tornadoes

Read everything you need to know about these violent storms also known as twisters.

Disasters explained: Droughts

Droughts affect millions of people each year. Learn what they and and how we’ve supported communities.

Boko Haram and the Lake Chad Basin crisis

Read how the conflict started, who is affected, and how ShelterBox is helping vulnerable families.

Ukraine crisis explained

Russia has launched a military operation on Ukraine. Read more about the crisis, who is involved, and get key facts.

Disasters explained: avalanches

Each year, avalanches kill over 150 people worldwide. Read more about avalanches, what causes them and more.

The crisis in Yemen

Yemen is the worst humanitarian crisis in the world. Learn more about the crisis here.

The Syrian Conflict Explained

Learn how the war in Syria began, who is involved and how families have been affected.

Hurricanes explained: The Saffir-Simpson Scale

The Saffir-Simpson wind scale is used to classify Atlantic hurricanes into 5 categories. Learn what that means.

Disasters explained: Earthquakes

Powerful earthquakes can be very deadly. Learn everything you need to know about earthquakes and how we help.

Disasters explained: Wildfires

Wildfires burn millions of acres of land every year. Find out more about what they are and their connection with climate change.

How does climate change affect disasters?

Climate change is a humanitarian crisis. Find out key stats about climate change, how it affects disasters and people, and what we’re doing about it.

Disasters explained: tsunamis

Tsunamis can destroy lives, homes, crops and roads in the blink of an eye. Learn more about what they are, what causes them and what the effects are.

Disasters explained: volcanoes

Learn what volcanoes are, how they erupt, and the effects of a volcano eruption.

Volcano eruption in Guatemala

In June 2018, Guatemala’s Fuego volcano erupted, affecting millions of people. It was the country’s most devastating volcanic eruption since 1974.

Hurricane Dorian

Everything you need to know about Hurricane Dorian, facts about hurricanes and how you can help.

Disasters explained: floods

Floods are among the most common and devastating disasters. Read more about why they happen and their effects.

Tracking Storms

See how we monitor and track hurricanes, cyclones and typhoons.

Disasters Explained

Everything you need to know about disasters – from extreme weather events to complex conflicts.