City dwellers face uneven heat exposure on the way to the subway

A circular image of a bridge has been covered with a purple tint. Above the image appears the AGU 2025 annual meeting theme (Where Science Connects Us), a wandering teal line representing a river and

Taking the train or subway can be a cost-effective and time-consuming way for city dwellers to get around. But during the summer months, some subway users risk exposure to extreme heat, the deadliest climate-related danger in the United Statesas you walk to and from the stations.

A team of researchers at George Mason University in Fairfax, Virginia, analyzed the surface temperatures of walkways within a 10-minute walk of the three busiest U.S. subway systems. Next, they considered how socioeconomic factors, such as age and race, and developmental patterns, such as parking spaces and interior hallways, were related to different levels of heat exposure.

The project started out of curiosity, he said. Luis Ortizurban climate scientist at George Mason University. “It combines two of my great passions,” he said. As a long-time urban heat researcher and avid public transportation user, Ortiz sought to answer a question from his daily life: “If you are a pedestrian using public transportation, what is your heat exposure like?”

Black, Asian, and Hispanic travelers experience greater exposure to extreme heat.

The scientists combined data on ridership at stations and Landsat 8 estimates of surface temperature to map where pedestrian transit users were most exposed to heat on the New York City Subway, the Washington Subway, and the Chicago “L.” ortiz will present the results on Dec. 16 at the AGU 2025 Annual Meeting in New Orleans.

The researchers found that the correlation between socioeconomic and demographic variables and surface temperatures was highest for the Chicago L and lowest for the Washington Metro. One pattern the researchers observed across the three cities is that travelers with minority identities, including Black, Asian and Hispanic travelers, experience greater exposure to extreme heat, the co-author said. Alireza Ermaguna transportation scientist. The same occurs with older populations and metro users between 25 and 44 years old.

Heat maps for surfaces within a 10-minute walk of three subway stations, one in New York, one in Washington DC, and one in Chicago. The New York example is the Rector Street station, which has a range of but mostly moderate surface temperatures. The example DC station is Downtown Largo and the surface temperatures are very high. The example season in Chicago is Harrison and temperatures are low to moderate. — The researchers analyzed surface temperatures within a 10-minute walk of a subway station in three US cities. Credit: Luis Ortiz, George Mason University

One result of the Washington Metro system seemed to contradict these correlations: Some of the most popular stations are in relatively wealthy areas of Northern Virginia. Investigators attribute the unexpected discovery to people driving to subway stations and parking a car. “They have huge parking lots there that get very hot in the afternoon,” Ortiz said.

A green solution

Urban planners should use research like this to strategize where to put shade and green space, he said. Nadav Spragueenvironmental epidemiologist at Harvard University who was not involved in the study. “Having access to shade is very important,” he said.

Many of the walking routes with high heat exposure have very few trees, Ortiz said. He said trees “solve several of the problems” that cause heat stress by providing shade, reducing heat radiation to the body and cooling the air.

“The best shade shelters are trees.”

Public transport users agree. “The best shady shelters are trees,” said Jasper Elysian, a student at the University of Illinois at Chicago who uses public transportation to get to school, work and just about everywhere else. When available, Elysian uses shade to beat the heat, but said they would like to see more trees near public transportation stops.

Quantifying heat exposure to understand who is exposed and how is important, Sprague said, because it is a hyperlocal problem that requires localized solutions. This research “gets to the point that every…place [faces] different implications of climate change”.

To better understand the specific challenges of each city, Ortiz and Ermagun said they want to collect more data on how often people in these cities in different socioeconomic situations use public transportation and whether this use is affected by the heat exposure they endure.

Recognizing that cities and counties have limited budgets, Ermagun hopes the team’s analysis will help decision-makers identify where funds can be most helpful in mitigating climate vulnerability. The ideal audience for this work, he said, is transportation designers.

—Pepper St. Clair (@pepperstclair.bsky.social), scientific writer

Citation: St. Clair, P. (2025), City dwellers face unequal heat exposure on the way to the subway, Éos, 106, https://doi.org/10.1029/2025EO250461. Published on December 15, 2025.

Text © 2025. The authors. CC BY-NC-ND 3.0
Unless otherwise noted, images are subject to copyright. Any reuse is prohibited without the express permission of the copyright owner.

#City #dwellers #face #uneven #heat #exposure #subway