Climate Matters
Urban Heat Hot Spots in 65 Cities
New Climate Central analysis shows where urban heat is most intense in 65 major cities that account for 15% of the U.S. population.
Climate Matters•June 25, 2025
Public Schools in Urban Heat Islands
KEY FACTS
The planet is warming due to human-caused climate change. In cities, the built environment further amplifies both average temperatures and extreme heat.
Heat is dangerous for everyone, but children face higher heat-related health risks than others.
Climate Central analyzed where urban heat and public schools intersect within the 65 largest U.S. cities, putting students at risk.
This analysis included over 12,000 K-12 public schools with nearly 6.2 million enrolled students.
About 76% of these students attend school in extreme urban heat islands — neighborhoods where the built environment adds at least 8°F more heat.
Across the nearly 6.2 million K-12 public school students included in this analysis, the average student attends school in neighborhoods that are 8.3°F hotter due to the built environment.
In nearly one-quarter of cities analyzed, nine in every 10 students attend school in an extreme urban heat island.
Keeping schools cool and students safe is a growing challenge as our climate warms.
This Climate Matters analysis is based on open-access data from multiple federal agencies, including the U.S. Census Bureau and the U.S. Department of Education. See Methodology for details.
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In largest U.S. cities, 76% of students attend public school in extreme heat zones
The entire planet is warming due to human-caused climate change, but the built environment further amplifies both average temperatures and extreme heat in cities.
According to the U.S. Environmental Protection Agency, “the urban heat island effect is a measurable increase in ambient urban air temperatures resulting primarily from the replacement of vegetation with buildings, roads, and other heat-absorbing infrastructure.
The combined effects of human-caused climate change and urban heat islands put heat-vulnerable populations — including children — at risk. And most U.S. public schools offer summer programming that keeps classrooms open during the hottest months of the year.
New Climate Central analysis estimated the exposure of K-12 public schools and students to urban heat islands within the 65 largest U.S. cities.
Explore interactive maps to see where public schools and urban heat islands intersect in each city.
This analysis expands on 2024’s Urban Heat Hot Spots in 65 Cities and covers the census-defined boundaries of each city. The analyzed areas:
are home to 50 million people, or 15% of the total U.S. population.
include 12,021 K-12 public schools with nearly 6.2 million enrolled students.
The majority (76%, or 4,680,558) of these students attend school in extreme urban heat zones, or neighborhoods where the built environment adds at least 8°F of additional heat.
In this Climate Central analysis, an extreme urban heat zone is defined as a census block group with an urban heat island (UHI) index of 8°F or higher. See Methodology for details.
The remaining 1.5 million students attend school in neighborhoods that are only slightly cooler.
Almost all (96%) of the nearly 6.2 million K-12 students included in this analysis attend public school in neighborhoods where the built environment adds between 6°F and 11°F of additional heat.
The average student attends public school in neighborhoods that are 8.3°F hotter
Across the nearly 6.2 million K-12 public school students included in this analysis, the average student attends school in neighborhoods that are 8.3°F hotter due to the built environment.
This ranges from a minimum of 7.3°F of additional heat for the average K-12 public school student in Phoenix, Ariz. to a maximum of 9.6°F in New York City, followed by: Newark, N.J. (9.1°F); San Francisco, Calif. (9.0°); Chicago, Ill. (8.7°F); and Philadelphia, Pa. (8.6°F).
Download data to explore UHI index rankings.
By comparison, the average resident of the 65 cities analyzed experiences 8°F of additional heat due to the built environment in their neighborhood.
Majority of students in extreme urban heat zones within 62 cities
More than half of all K-12 students attend public school in extreme urban heat zones within 62 of the 65 cities analyzed. The three exceptions were: Boston, Mass. (where 36% of students attend school in extreme urban heat islands); Providence, R.I. (42%); and Richmond, Va. (49%).
At least nine in every 10 students attend public school in extreme urban heat zones within 15 cities (nearly one-quarter of cities analyzed).
The 10 cities with the highest proportion of K-12 students attending public school in extreme urban heat zones include smaller cities that may have fewer resources to address the widespread burden of urban heat on public schools and students.
City | Percent (number) of K-12 students attending public school in extreme urban heat zones |
|---|---|
Louisville, Ky. | 98% (32,384) |
Wilkes Barre, Pa. | 97% (3,857) |
Orlando, Fla. | 97% (43,733) |
West Palm Beach, Fla. | 95% (17,861) |
Newark, N.J. | 95% (56,459) |
Houston, Texas | 94% (326,596) |
Norfolk, Va. | 93% (25,278) |
Cleveland, Ohio | 92% (48,828) |
Tampa, Fla. | 92% (54,294) |
Sacramento, Calif. | 92% (75,282) |
Largest cities have the most students in extreme urban heat zones
The top 10 cities with the most students attending school in extreme urban heat zones are also the 10 largest U.S. cities in terms of population.
Each of these cities has at least 100,000 K-12 students attending public school in extreme urban heat zones.
City | Number (percent) of K-12 students attending public school in extreme urban heat zones |
|---|---|
New York, N.Y. | 819,719 (85%) |
Houston, Texas | 326,596 (94%) |
Los Angeles, Calif. | 279,495 (65%) |
San Antonio, Texas | 227,707 (91%) |
Chicago, Ill. | 213,723 (66%) |
Dallas, Texas | 188,838 (91%) |
Phoenix, Ariz. | 142,306 (55%) |
San Diego, Calif. | 130,463 (78%) |
Austin, Texas | 108,125 (87%) |
Philadelphia, Pa. | 103,962 (58%) |
Extreme urban heat puts students at risk
Heat is dangerous for everyone. It’s the deadliest weather-related hazard in the U.S. But children (aged 0-17 years) are among those most vulnerable to heat-related health risks.
Learn more: Climate Change & Children's Health: Extreme Heat
Extreme heat affects children’s health and development. It can disrupt sleep, affect mood, and impact the ability to concentrate and learn. Studies show that heat exposure is associated with reduced academic achievement.
And while the school year doesn’t typically include the hottest months of the year, 82% of U.S. public schools offer summer programming, most of which aims to help students academically.
During extreme heat events, the urban heat island effect can worsen heat stress and related illness, put vulnerable populations including children at risk, and lead to higher energy bills and strained power grids during spikes in cooling demand.
These risks aren’t felt equally. Studies have shown that urban heat islands are more likely to be found in predominantly lower-income and non-white communities. Unequal urban heat burdens are also linked to a history of racially biased housing policy. Historically redlined areas currently experience hotter summers than non-redlined areas in 150 major U.S. cities.
Cooling is critical, and demand is rising
A 2024 analysis by Climate Central found that cooling demand during the back-to-school period has increased since 1970 in 231 U.S. cities, and that human-caused climate change is driving the rise.
Learn more: Cooling Schools in a Hotter Climate
Access to cooling is critical to ensure the health, safety, and well-being of students and school staff in our rapidly warming world. But schools across the U.S. lack adequate infrastructure to cool buildings. An estimated 41% of public school districts need to replace or update HVAC systems in at least half of their schools.
The average U.S. public school is about 50 years old. These facilities were not built to function in our present-day climate. Rising temperatures (and therefore increased cooling demand) will bring necessary school upgrades, as well as higher maintenance and operations costs to keep students and staff cool.
Urban heat outside the classroom
Extreme urban heat can also affect students outside the classroom — on playgrounds and sports fields.
Learn more: More Extremely Hot Days for School Sports
Young children sweat less and acclimate to heat more slowly than adults, and children may ignore or miss symptoms of heat stress.
And as our planet warms, extreme heat events occur more often and are expanding beyond the summer into months when school is in session.
Protecting kids from heat impacts
Teachers, coaches, and caregivers can protect children’s health by reducing exposure to dangerous heat at home, at school, and during outdoor activities.
Check temperature and heat risk forecasts and note heat advisories or excessive heat warnings.
Avoid outdoor activities during the hottest part of the day (usually midday).
Plan to take frequent breaks in the shade or air-conditioned spaces.
Make sure kids drink enough water during outdoor play or sports.
Know the symptoms of heat-related illness and be prepared to take action.
Without effective measures to adapt to a warming world, children will experience worse health impacts –- including a potential increase in heat-related emergency room visits.
Future generations are likely to face accelerating change and intensifying risks — particularly from heat waves — with continued warming.
Ultimately, a commitment to rapid, sustained cuts to carbon pollution is the most impactful action to slow the rate of warming and set younger generations on a different path, toward a safer future.
Why it’s hotter in the city
Several key factors that affect heat in cities were included in the UHI index (see Methodology):
The three biggest factors that influence UHI index are, in order:
Albedo is the fraction of sunlight (solar radiation) that a surface reflects. Hard, dark surfaces (roads, buildings, parking lots) have low albedo. This means that they absorb (rather than reflect) a higher portion of incoming sunlight and radiate it back into the city as heat. Of all the factors used to calculate UHI index values, albedo generally has the largest influence.
Green space. Plants help cool the air through evapotranspiration. Less vegetation means less cooling. Plants can help reduce peak summer temperatures by 2°F to 9°F in urban areas. Learn more: The Power of Urban Trees.
Population density. Extra heat also comes from human activities: transportation, industrial facilities, and the cooling of buildings. During a heat wave, air conditioning can add 20% more heat to the outside air.
Other characteristics of the built environment, including the width of streets, orientation of urban canyons, and building heights have a smaller relative influence on UHI index estimates.
LOCAL STORY ANGLES
How are heat islands being addressed in your city?
Find relevant information for all 65 cities in this analysis here to help answer questions such as: Does your city have an official heat action plan? What resources are available to vulnerable residents during heat waves? And what is your city doing to cool itself down?
See how your city’s parks stack up
See where your city falls in the Trust For Public Land’s ParkScore that ranks the top 100 most populous U.S. cities on five categories reflective of an excellent park system: acreage, access, equity, investment, and amenities. Parks and green space are effective mitigators of urban heat islands.
FIND EXPERTS
Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts.
Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.
Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices.
Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area.
METHODOLOGY
A 2024 Climate Central analysis, Urban Heat Hot Spots in 65 Cities, calculated the urban heat island (UHI) index in 37,094 census block groups (divisions within census tracts that each contain around 600 to 3,000 people) across 65 large U.S. cities. The combined population of these 65 cities is over 50 million, or about 15% of the total U.S. population. Census Places, statistical entities defined by the U.S. Census, were used to define city boundaries.
UHI index values (in °F) are estimates of how much the urban built environment boosts temperatures. In other words, the UHI index is an estimate of the additional heat that local land use factors contribute to urban areas.
For example, on a 96°F day in rural northern Texas, people living or working in a Dallas neighborhood with a UHI index value of 9°F would experience temperatures of at least 105°F.
Climate Central adapted the modeling approach of Sangiorgio et al. (2020) to calculate UHI index values for each census block group based on the prevalence of different land cover types and parameters of the built environment in each census block group. The land cover types included in this analysis cover a range of six natural (excluding open water) and 10 built environments, as classified by Demuzere et al. (2020). Climate Central applied the model developed by Sangiorgio et al. (2020) to weight each census block group’s land cover types and parameters of the built environment and calculate the UHI index for that block group, as described in the detailed methodology available here.
In this analysis, Climate Central defined “extreme urban heat zones” as census block groups with an UHI index of 8°F or higher. The 8°F threshold was selected because it is the per capita average UHI index experienced by residents of the 65 cities analyzed, as reported in Urban Heat Hot Spots in 65 Cities. Extreme urban heat zones are therefore areas with urban heat intensities above the per-capita average.
Public school characteristics for the 2022-23 school year (the most recent data available as of 6/18/2025) were obtained from the National Center for Education Statistics' (NCES) Education Demographic and Geographic Estimates. All 12,021 public K-12 schools located within the census-defined boundaries of the 65 major cities assessed in Climate Central’s UHI Index analysis were included; the total enrolled students across these schools (during the 2022-23 school year) is 6,157,062. The population-weighted average UHI index (across all 6,157,062 enrolled K-12 public school students) is 8.3°F. Private schools were excluded from this analysis.