Extreme heat poses growing risks across cities and neighborhoods

Urban surfaces and less tree cover make some city neighborhoods several degrees hotter, and research finds access to cooled public spaces is linked to fewer heat-related deaths while fans can be ineffective above about 95°F.

Researchers at UCLA describe extreme heat as a growing public health threat concentrated in some urban neighborhoods. Urban surfaces such as asphalt and roofs absorb and re-radiate heat, leaving dense, low-canopy areas warmer by several degrees and warmer at night. The issue is tied to unequal neighborhood conditions and to broader climate-driven increases in both heat and wildfire smoke. Key findings: - Urban surfaces and dense development create an "urban heat island" effect, causing some neighborhoods to be several degrees hotter and to retain heat at night. - Excess emergency visits during heat events cluster in lower-income, lower tree-canopy and formerly redlined neighborhoods; Latino and Black communities are reported as more likely to be at higher risk. - At or above roughly 95°F, research notes that fans can be ineffective or harmful; cold water applied to high-vascular areas and access to air-conditioned spaces are cited as more effective immediate cooling approaches. - Access to cooled public spaces is linked to lower heat-related mortality: census tracts with the least access saw a reported 38% increase in heat deaths per 1°C rise in maximum temperature, and measures like increased tree canopy and more reflective surfaces can lower temperatures by up to 2°C and could reduce 25–50% of excess ER visits in plausible scenarios. Summary: Heat and wildfire smoke are both described as underrecognized, climate-driven causes of premature death, and recent research suggests smoke may now account for more deaths in California than heat. Undetermined at this time.