Heat waves: How to cope with new extremes

The Explainer

It’s hot out there, and it’s getting hotter.

Temperatures broke June records around the globe, from the leafy streets of the American South to the domes of the Vatican. Japan recently had its first-ever 104-degree June day. Cities across Iran have sweltered for days under 122-degree heat. It was even hot above the Arctic Circle, where thermometers in the Russian city of Norilsk pushed to record highs grazing 90 degrees. 

In the U.S., states across New England and the Mountain West are in for unusually high heat through the end of the summer, according to an analysis by the National Weather Service’s Climate Prediction Center.

These waves of extreme heat pose serious public health challenges. A heat wave that began a year ago this week in the Pacific Northwest contributed to hundreds of deaths. And the World Health Organization attributes 166,000 deaths globally to heat waves over a period stretching from 1998 to 2017.

Modern comforts like air conditioning have mitigated heat’s direst effects. For the last 50 years, for example, heat-related deaths in the United States have generally been declining, according to a 2021 study. But the same study cautions that, in the last decade or so, the decline has slowed, and possibly even started to reverse.

With heat waves growing longer, hotter, and more frequent, scientists and officials are exploring ways to keep people safe.

What counts as a heat wave? 

There’s no single definition, but generally a heat wave is when abnormally high heat lingers for two or more days. It’s not just a matter of how hot it is, but also of how unusual that temperature is. Even in a state like Nevada that’s used to triple-digit summers, stretches when it’s 115 degrees can cause distress.

Consecutive days of extreme heat, when overnight temperatures stay high, exacerbate vulnerabilities. “The most dangerous part,” says P. Grady Dixon, a professor at Fort Hays State University and author of that 2021 study, “is the lack of cooling off.” 

Who’s most vulnerable to extreme heat?

Historically, older adults have been most at risk. However, over the past few decades, they’ve benefited greatly from the spread of air conditioning and more effective messaging to deliver heat warnings. According to Dr. Dixon, their safety has helped improve U.S. health statistics related to heat’s dangers.

But not everyone can take advantage of AC. For instance, homeless people or day laborers who spend their days outdoors are increasingly vulnerable to extreme heat.

Urban landscapes can also worsen heat. Asphalt streets, tightly packed buildings, lack of green space, and gas-powered engines create so-called urban heat islands. This is evident in Boston, where a 2019 city study found the Chinatown neighborhood, which is downtown, was up to 12 degrees hotter than leafier suburbs.

How do we keep people safe? 

The simplest and most important step toward safety is knowing when there’s a risk.

“When the weather forecast [on your phone] is a smiley face or a rain cloud, that’s not good enough,” Dr. Dixon urges. “Seek out the National Weather Service and heed their heat warnings.”

Kimberly McMahon, a program manager at the National Weather Service, says the agency is working to develop even better warning tools that can single out what is dangerous for specific areas or populations.

Another priority is making sure those messages reach everyone who needs them – including non-English speakers and people who spend their days working outdoors.

“We’ve done video PSAs in English and Spanish. Radio in English, Spanish, and Creole. Billboards at bus stops, particularly targeting the ZIP codes with the highest severe heat,” says Jane Gilbert, a Miami official.

Ms. Gilbert is herself an example of how cities are pushing to mitigate heat. She’s Miami-Dade County’s chief heat officer, a position created to coordinate efforts to cool cities. Ms. Gilbert was the first, appointed in June 2021, and Phoenix and Los Angeles have each appointed ones since. 

Another step toward safety is to keep vulnerable people out of harm’s way.

Erick Bandala of Nevada’s Desert Research Institute says places “need stricter regulations [to protect] workers who have no choice but to go out there and work even on a 110, 115 [degree day].”

Communities across the country have opened cooling stations: libraries, community centers, senior centers, and other spots open to anyone who needs shelter from the dangerously hot outdoors.

Cities are making more permanent transformations as well. Since 2009, New York City has repainted tens of thousands of dark rooftops white to stop them from absorbing so much heat. And Los Angeles has begun covering its endless asphalt streets with a reflective coating.

Meanwhile, nearly every city is striving to plant more trees, which offer much-needed shade. “We’re giving away over 10,000 trees this summer,” says Ms. Gilbert, continuing local initiatives that have planted more than 218,000 trees since 2001.

In some ways, the U.S. is playing catch-up with places like Singapore that have long committed to tackling heat. The equatorial country has central cooling systems, rooftop gardens, and greenery that scales the sides of tall buildings.

Kathy Baughman McLeod, director of the Adrienne Arsht-Rockefeller Foundation Resilience Center at the Atlantic Council in Washington, sees hope in her work promoting heat mitigation efforts around the world.

“There are a lot of aspects of climate change that feel intractable,” she says, “but this is not one of them.”