Paris Staged a Huge Stress Test for Extreme Heat
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Paris Staged a Huge Stress Test for Extreme Heat
A two-day simulation drew thousands of participants — and revealed important lessons for how cities can rise to meet a hotter future.
By:<br>Natalie Donback
May 8, 2026 8 min read
Paris Staged a Huge Stress Test for Extreme Heat
A two-day simulation drew thousands of participants — and revealed important lessons for how cities can rise to meet a hotter future.
By:<br>Natalie Donback
May 8, 2026 8 min read
Cities + Towns
Credit: Ludovic Marin / AFP via Getty Images / Grist
This story was originally published by Grist. Sign up for Grist’s weekly newsletter here.
On a sunny Friday afternoon in October 2023, some 70 children filed into a cool, dark tunnel in the south of Paris to help the city rehearse for its increasingly hot future.
The tunnel, part of the abandoned Petite Ceinture railway encircling the city, is always 64 degrees Fahrenheit (18 degrees Celsius), making it the perfect safe haven from the potentially lethal heat imagined outside. Once underground, each youngster was asked to simulate the effects of extreme temperatures that might become reality in their lifetimes. Some pretended to have been poisoned by food that spoiled during a power outage. Others faked the effects of carbon monoxide leaking from a faulty generator. Meanwhile, Red Cross workers scrambled to decide who to send to overwhelmed hospitals. Around them, dozens of others — fire fighters, city officials, teachers — did their best to simulate the chaos and cascading impacts a heat wave of unprecedented duration and intensity might force them to confront.
The officials who created the Paris at 50C exercise wanted children to participate because they will face the consequences of a warming world and because they ask so many questions. Courtesy of Crisotech<br>The exercise, called Paris at 50 degrees Celsius, was designed to imagine what might happen if the mercury hits 122 degrees F, something scientists warn is increasingly likely by 2100. It combined live drills and a tabletop exercise to help shape a plan to protect the city’s two million people from that kind of heat. Once limited to a handful of cities, these exercises are spreading as local governments stress test health services, emergency response, and essential infrastructure before temperatures reach dangerous extremes.
What Paris is rehearsing could soon confront cities across the continent. European governments are being urged to prepare for 5 to 6 degrees F (2.8 to 3.3 degrees C) of warming, a change that could push Paris toward dangerous summertime temperatures by the end of the century.
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Such heat is a global threat. Modeling suggests more than 1.6 billion people in nearly 1,000 cities could regularly face perilous conditions within three decades. Heat waves are already straining hospitals, causing outages and paralyzing transit. In the complex systems that make up a city, even small failures can lead to larger breakdowns.
But as cities invest time and money into these exercises, one question remains: Do they actually improve preparedness?
It took Pénélope Komitès more than 18 months to prepare a drill that would last just two days. As Paris’ deputy mayor in charge of resilience, she considers such planning essential. “It was very important for us to show people that heat waves are not just something we see on the TV, but something that can happen soon, and that we need to improve what we’re going to do,” she said.
To help inform the scenario, scientists at the Île-de-France Regional Climate Change Expertise Group, which advises city leaders on climate risk, modeled what the future might look like. Other studies based on data from the Intergovernmental Panel on Climate Change have largely confirmed their projection that temperatures could hit 122 degree F (50 degrees C) by the end of the century. For now, the city’s record stands at 108.68 F (42.6 C), registered on July 25, 2019.
A temperature sign over a pharmacy in Paris, France, reads 47 degrees C (116 degrees F) during a heat wave in 2015. Credit: Pierre Suu / Getty Images / Grist<br>The World Health Organization estimates that heat contributes to roughly half a million deaths worldwide each year. Symptoms can quickly escalate from fatigue to dehydration to heat stroke as the body loses its ability to cool itself. For older adults and people with heart or kidney disease, that strain can be fatal.
In Paris, much of the work of designing the simulation fell to Crisotech, a consultancy specializing in crisis exercises. It spent nine months working with the city to develop a dozen scenarios designed to anticipate where services would buckle, how agencies would work together and which residents might be missed. The role-playing the children, from two different...