How Local Heat Exposure Shapes Mortality in Cities

As climate change intensifies, cities around the world are investing in neighborhood-level measures to protect residents from extreme heat. But how much do local temperature differences within cities matter for public health?

A recent IZA Discussion Paper by Vinicius Peçanha, Rudi Rocha and Dimitri Szerman provides the first evidence that heat-related mortality is largely driven by highly localized heat exposure—and that adaptation policies must combine neighborhood-based interventions with city-wide preparedness.

Satellite Data Reveals Local Hotspots

The study examines the relationship between extreme heat and mortality in Rio de Janeiro using a unique dataset that combines high-resolution satellite temperature measurements with geocoded administrative mortality records. This approach allows the authors to measure temperature exposure at the neighborhood level, revealing substantial variation in heat across the city that conventional weather station data cannot capture.

Consistent with a large body of evidence showing that temperature has a U-shaped relationship with mortality, the study finds that additional hot days significantly increase deaths among older adults. Remarkably, nearly 60 percent of the estimated heat-related mortality effect is explained by localized differences in temperature exposure across neighborhoods rather than by city-wide heat shocks.

The authors also show that neighborhoods become increasingly similar in temperature as average heat rises. During extreme heat events, exposure converges across the city, reducing the importance of local temperature differences while increasing the role of common city-wide heat shocks.

Preventive Care vs. Emergency Response

The paper further investigates whether local health services can mitigate these effects. Exploiting the staggered expansion of Rio's Family Health Program and emergency care facilities, the authors find that both preventive primary healthcare and proximity to emergency services reduce heat-related mortality during city-wide heat waves. However, when mortality is driven by localized exposure differences, only proximity to emergency services continues to provide significant protection.

The findings suggest that climate adaptation strategies should not rely solely on neighborhood-level interventions. While localized measures remain important, increasingly severe heat waves require coordinated city-wide preparedness and resilient emergency healthcare systems to protect vulnerable populations.

By highlighting the importance of within-city differences in climate exposure, the study advances our understanding of how extreme heat affects urban populations and provides new evidence to inform the design of effective public health adaptation policies in a warming world.

Download the full paper here.