San Antonio's urban heat islands, mapped
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San Antonio is facing growing health risks from urban heat islands, which can exacerbate life-threatening temperatures.
Why it matters: Tracking urban heat islands helps identify at-risk communities and inform strategies to ensure public health as Texas moves into the peak of summer.
How it works: Heat islands are created when roads, buildings and parking lots trap heat.
- Surrounding neighborhoods often lack trees that would otherwise help cool the area.
- Low-income neighborhoods tend to be more vulnerable to heat islands than wealthier ones, making this a key climate equity issue.
The big picture: Urban heat island (UHI) indices are boosting temperatures in 65 major U.S. cities, which are home to a combined 50 million people or 15% of the total U.S. population, according to a new analysis by Climate Central, a nonprofit research group.
Zoom in: In San Antonio, 88% of the population lives in areas where urban heat islands can raise summer temperatures by at least 8°, per Climate Central.
- It's one of six cities where at least 1 million people are exposed to a UHI index of 8° or higher. The difference could mean life or death in extreme heat.
- San Antonio hit 106 — the hottest days of 2023 — in July and August.
Threat level: San Antonio is seeing an increasing number of heat-related illnesses — at least 787 last year — as summers grow hotter, according to city data.
The intrigue: The worst of San Antonio's heat islands are scattered around the city — deviating from national norms that typically see the brunt borne by lower-income neighborhoods that often lack foliage to cool the area.
- Downtown, from East César E. Chávez Boulevard to Navarro Street, is the single hottest section in town where the UHI index raises the temperature by 9.7°F.
What they did: The City of San Antonio partnered with UTSA's Sustainable Pervasive Urban Resilience (SPUR) Center to track heat vulnerability and allocated resources to the most impacted areas.
- The partnership is an expansion of the Cool Pavement Pilot, which helps cool neighborhoods by treating asphalt to better reflect sunlight and absorb less heat.
- The program treated roads in each of the city's 10 districts last year and has 11 more applications planned for this year.
What they found: The heat vulnerability study identified the most at-risk neighborhoods for extreme heat by combining geographical data with factors like income and race to determine vulnerability.
- The study found that SealMaster, a cool pavement technology, consistently reduced surface temperatures by an average of 3.58°.
- It lowered the maximum surface temperature by 18° compared to conventional asphalt.
What's next: The city is using the findings to guide its heat response strategy, which includes activating cooling centers like swimming pools and senior centers.