A prolonged heatwave that began in Mexico and the U.S. Southwest is slated to continue to spread East this week and could endure through the end of June over much of the country. This expansive heat dome will affect people in most of the lower 48 states and Puerto Rico at some point over the next couple of weeks with many places expecting days when the “feels like” temperature exceeds 100 degrees Fahrenheit.

Extreme heat, especially over such an extended period of time poses particularly grave risks to those experiencing poverty or homelessness, people (often people of color) living in urban heat islands, elderly adults, small children, people with cardiovascular and other health conditions, outdoor workers, and people facing electricity shut offs or lacking reliable access to air conditioning. High demand for air conditioning also increases the risk of electricity prices spikes, outages, and increased pollution from fossil fuel-fired power plants.

Nearly 80 million people in the United States and its territories are threatened today by what the Union of Concerned Scientists (UCS) has deemed “Danger Season”—the time roughly from May through October in the Northern Hemisphere when climate change impacts in the United States are at their peak and increasingly likely to coincide with one another. Additionally, 72% of extreme heat alerts since May 1, 2024, were made more likely by climate change. These data are according to the UCS Danger Season map, which tracks daily heat, wildfire weather, storm, and air quality alerts.

“We are living in a perilous and precarious world that has been warmed by more than 1 degree Celsius because of decades of dependence on fossil fuels, decades of deception and obstruction by the fossil fuel industry, and decades of inaction by policymakers who have been in their thrall,” said Dr. Kristina Dahl, a principal climate scientist at UCS. “Fossil fuel-driven climate change has increased the frequency and severity of extreme-heat events over the last half century. Last summer was the hottest on record, and this summer is shaping up to give 2023 a run for its money. Until we phase out fossil fuels, we can expect our summers to continue getting hotter and hotter and more dangerous and deadly.”

There are actions national, state, and local policymakers can take right now to better protect people. These should include implementing local emergency heat safety plans that entail heat alerts, access to community cooling centers, and other health-protective measures for those most vulnerable to heat. Preventing utility shutoffs during times of extreme weather including heatwaves like this one and implementing commonsense safeguards to ensure outdoor workers have access to shade and water, as well as more frequent rest breaks, is also vital. But ultimately, limiting the number of days of extreme heat in the long term necessitates that policymakers and decisionmakers in all sectors of society do their part to phase out fossil fuels and accelerate the transition to a clean and just energy system.  

Last week, a group of more than 750 scientists sent an open letter, organized by UCS, to Citi CEO Jane Fraser and Board Chair John Dugan, urging the company to stop financing new fossil fuel projects. The letter is part of the “Summer of Heat on Wall Street” campaign.

Additional UCS Resources and Analyses:

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet’s most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future. For more information, go to www.ucsusa.org.