Horizon, person on beach bending over in heat

Extreme heat, explained: How a warming world makes heat waves worse

Climate change is scorching the globe, including areas previously thought to be low-risk.

And the firsts keep coming, with record-breaking daytime highs in many places, plus sweltering nights — all of which take an especially brutal toll on those without air conditioning, outdoor workers, older people, children and many who have health issues.

According to the World Meteorological Organization, “2025 was one of the three warmest years on record, continuing the streak of extraordinary global temperatures.”

How are climate change and heat waves connected?

There is a clear link between climate change and heat waves: Climate change has increased the probability of heat waves and made them more frequent and intense. Heat waves are also lasting longer, on average, research shows.

Climate change can make heat waves worse via changing air patterns that set up ideal conditions for “heat domes,” where hot air is trapped on Earth’s surface by high pressure buildup in the atmosphere.

Scientists are finding that in many places, extreme heat events that would once have been rare are now much more likely to occur.

Learn more about climate change and extreme weather

Heat is one of the deadliest weather hazards

In Europe, which is warming faster than any other continent, researchers estimate that tens of thousands of people died from heat-related causes between June and September each year in 2022, 2023 and 2024.

It’s important to keep in mind that a hot day feels even hotter when it’s humid, increasing the risk of heat-related illnesses ranging from heat exhaustion to heat stroke. At just 70% humidity, 96 degrees Fahrenheit feels like 126 degrees — and that’s in the shade.

It’s also important to know that air pollution can be worse on hot days, creating another health concern.

How severe heat disrupts daily life

Here are a few ways we’re feeling the effects of extreme heat:

  • Droughts and wildfires: Hotter temperatures mean more — and more persistent — droughts in already drought-prone areas due to increased evaporation. And that can trigger yet more problems, as severe heat and drought can fuel the risk of catastrophic wildfires.
  • Schools: Heat is hurting kids’ education as sweltering temperatures prompt schools to cancel classes or let out early. Many classrooms don’t have air conditioning, and research has shown that heat can make it harder to learn.
  • Agriculture: Extreme heat endangers farmers’ livelihoods as well as their health. And rising temperatures threaten the availability of food by putting stress on livestock and increasing the likelihood of crop failure in some areas.
  • Workers’ health: In addition to farmworkers, people who work outdoors in industries like construction are at risk when temperatures spike. Indoor workplaces like kitchens and warehouses can also heat up dangerously if protections aren’t in place.
  • Sports: Extreme heat poses risks to athletes as well as officials and fans. This affects sports at all levels, from youth sports to the Olympics.

What can we do about extreme heat?

As heat waves get worse, solutions for combating extreme heat can take many forms. These include keeping homes cool; putting strong policies in place to protect workers; supporting farmers and ranchers; making sure athletes and coaches have information on ways to stay safe while exercising; and much more.

Looking ahead, we know why our climate is changing.

Human activities — like burning oil, gas and coal — are releasing large amounts of greenhouse gases like carbon dioxide and methane into the air. And because these gases trap heat in the atmosphere, the Earth is getting dangerously warmer.

To protect lives today and safeguard future generations, we must reduce greenhouse gas emissions aggressively, without delay.

Learn more about climate change and extreme weather