Recent Surge in Extreme Heat Events in São Paulo

São Paulo, Brazil's largest metropolis with over 12 million residents, has faced increasingly frequent and intense heatwaves in recent years. In January 2026, the city recorded a staggering 36.4°C in the Mooca neighborhood on the East Side, marking one of the highest temperatures ever observed. This extreme heat is not isolated; urban heat islands (UHIs)—areas where concrete and asphalt trap heat, raising temperatures 2-10°C above rural surroundings—exacerbate the problem. The Surface Urban Heat Island (SUHI) effect, measured via satellite data, shows São Paulo's core and peripheries heating up faster than greener outskirts.

These events align with broader climate trends. Brazil has seen nearly 50,000 heat-related deaths over the past two decades, with global figures reaching 550,000 annually. In São Paulo, the interaction between urbanization, climate change, and local weather patterns like the South Atlantic Subtropical Anticyclone (ASAS) can intensify UHIs by up to 5°C, expanding their reach by 697% toward the periphery.

USP's Pioneering Heat Risk Mapping Study

Researchers at the University of São Paulo's Faculty of Architecture and Urbanism (FAU-USP) have produced the first spatially explicit heat risk map for São Paulo at the census tract scale. Published in Urban Climate (2025), the study by Luiza Sobhie Muñoz, Denise Helena Silva Duarte, and Rohinton Emmanuel defines heat risk using the IPCC framework: Risk = Hazard × Vulnerability × Exposure / Adaptive Capacity.

Using open public data from satellites (land surface temperature, soil impermeability), IBGE census (income, age demographics, population density, housing types), and expert input, the map reveals high-to-extreme risk concentrated in favelas and peripheries of the East, North, and South zones. These areas feature high SUHI intensities, low vegetation cover, high density, low income, and higher proportions of vulnerable groups like children and the elderly.

The novelty lies in incorporating subtropical-specific parameters: housing type (formal vs. informal/favela), urban morphology, and vegetation proximity—factors overlooked in temperate-focused models. Central and high-income areas show lower risk due to better adaptation (parks, AC access).

Urban Heat Island Effect: Drivers in São Paulo

São Paulo's SUHI is driven by rapid urbanization: over 3,000 km² impervious surfaces reduce evapotranspiration, boosting sensible heat flux. Studies from Unicamp's NEPO highlight how the city's expansion—projected to grow 38% by 2030—overlaps with risk zones, intensifying heat in low-lying valleys like Tietê and Pinheiros rivers.

Unesp and Unicamp research on medium-sized cities near SP shows even smaller urban areas generate UHIs up to 6.7°C, underscoring regional vulnerability. IEA-USP analysis defines heat extremes as >32°C (comfort 14-26°C), with ASAS positioning amplifying central-peripheral heat spread.

• Impervious surfaces: Asphalt/concrete retain heat, reducing cooling by 160-250 W/m² latent flux.
• Low greenery: Peripheries lack parks, worsening exposure.
• Population density: >3,197 hab/km² in core areas heightens collective risk.

Social Inequality Amplifies Heat Vulnerability

The USP map starkly illustrates 'climate inequality': favelas like Paraisópolis experience 8°C hotter conditions than affluent Morumbi nearby. Low-income residents in informal housing lack AC, ventilation, or shade, while outdoor informal jobs increase exposure. Children, elderly, and low-income groups (often Black/indigenous) face compounded risks.

Only 35% of SP has high climate mitigation capacity (tree cover), concentrated in wealthy zones. Peripheries have minimal protection, perpetuating a feedback loop: poverty limits adaptation, heat worsens health/poverty.Explore higher ed career advice on climate resilience roles.

Photo by Ian Talmacs on Unsplash

Health Impacts: Cardiovascular Strain and Mortality

Extreme heat triggers cardiovascular events, dehydration, and heatstroke. In SP state, heat correlates with excess mortality, especially in vulnerable subgroups. Nationally, heat waves contributed to up to 55,000 urban deaths (2000-2018). Hosp costs from heat exceed $87M annually in 2010s; projections under 2-3°C warming amplify this.

2026's early heat already spiked infarts 40%, surpassing cold-day risks. Elderly/cardioresp patients in hot favelas bear brunt.Read the full USP study

Educational Disruptions: Heat and School Dropout

FGV Brazil and Minerva University (US) study in Nature Climate Change (2025) analyzed 30,000 schools: each additional day >34°C raises public high school dropout 5%, urban low-income/Black students hardest hit. Private schools mitigate via AC. Heat impairs cognition, sleep, attendance—deepening inequalities.

In SP, sweltering classrooms (up to 42°C Rio analog) cause desmaios, evasion. Universities like USP advocate heat-proof schools.Rate professors researching climate education impacts

Future Projections: Doubled Warming in Urban Brazil

PNAS study (2026, UEA-led) warns tropical cities like SP could warm twice rural rates under 2°C global limit—81% affected. Low-res models underestimate; machine learning/satellite data show humid nights/extremes surging. RMSP projections: +2-4°C, intense rains +20-50%, heat days ×15/year.

Productivity losses: 512B hours globally 2023 ($835B); Brazil GRP dips 2.1pp/decade.

Nature-Based Solutions: Cooling São Paulo by 5°C

USP/Biota/IPA study: Arborization, parks expansion, green corridors, rain gardens cut thermal sensation 5°C. SP's Refloresta-SP boosts tree cover; only 35% territory protected now. Unicamp recommends várzeas restoration, permeable surfaces.

• Tree planting: +vegetation proximity halves risk.
• Green corridors: Link parks, reduce UHI spread.
• Urban forests: 410k ha potential fringe restoration.

Government NbS report (USP contrib)

Photo by Joao Alves on Unsplash

Policy Recommendations and University Roles

FAU-USP urges integrated policies: prioritize favelas for greening/housing upgrades. Replicate risk maps nationally. Economic: Heat costs GDP via health/labor; NbS yield ROI via resilience.

Brazilian universities lead: USP/IEA mapping, Unesp UHI medium cities, Unicamp megacity vulns. Careers in climate adaptation booming—Explore research jobs in Brazil higher ed.

Conclusion: Urgent Action for Equitable Resilience

Extreme heat risk in São Paulo demands immediate, equity-focused response. USP's map spotlights injustice; projections warn escalation. Nature solutions offer hope, backed by rigorous uni research. For professionals, opportunities abound in climate HE: Rate climate profs, Find higher ed jobs, Career advice, University jobs Brazil. Act now for cooler, fairer future.