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HEATWAVES AND HEALTH RISKS IN NEW YORK CITY

Amanda Liang, Sarah Wu

February 11, 2026

ISBN: 979-8-89480-841-3


Heatwaves, locally defined as having at least three consecutive days with temperatures exceeding 90 °F, pose a significant and growing risk to public health in New York City (NYC), particularly as climate change intensifies their frequency and severity. Rising global temperatures have led to more prolonged and intense heatwaves that exacerbate health risks, especially for vulnerable populations. The urban heat island (UHI) effect further exacerbates these risks by increasing localized temperatures in densely built environments. As extreme heat events have increased in NYC, the health burden associated with them has become a pressing concern. The heatwave season now lasts significantly longer than in past decades, contributing to hundreds of heat related emergency department (ED) visits and hospitalizations each summer. Consequently, emergency response systems face increased strain. This study seeks to quantify the relationship between heatwaves and heat related ED visits and project future health impacts under different climate scenarios.

The analysis incorporates NYC historical climate and air pollution data, along with ED visit records from May to September during 2017–2023. Climate projections (2015–2100) are derived from 21 CMIP6 climate models under three Shared Socioeconomic Pathways (SSPs) (SSP 2-4.5, SSP 3-7.0, and SSP 5-8.5) that model different greenhouse gas emissions and climate change scenarios. We defined various climate measures related to temperature, humidity and air pollution and examined their correlation with heat-related ED visits. We further used a distributed lag non-linear model (DLNM) with quasi-Poisson regression to assess the potentially nonlinear and delayed effects of each candidate risk factor on heat-related ED visits. The best fitted model, identified by the smallest deviance, suggested that daily maximum temperature is the best predictor. Fitted values from this model estimated the relative risk of heat-related ED visits during heatwave conditions to be as high as 7.93 with 95% CI (7.71, 8.16), indicating that heatwaves are a significant risk factor for heat-related ED visits. Assuming the expected number of heat-related ED visits during non-heatwave days does not change over time, future projections of heat-related ED visits in 2075 2100 were calculated using both estimated relative risk and the projected increase in total heatwave days compared to 2017 2023 based on different climate models. The medical cost of these events is projected to range from $70 million (under SSP 2-4.5) to $1.2 billion (under SSP 5-8.5). If effective risk mitigation strategies successfully reduce the daily maximum temperature by 0.5-1 °C, then the maximum medical cost for all heat-related ED visits in 2075-2100 would be reduced by $137-$286 million. If combining adaptation, increasing in public awareness and other effective risk mitigation strategies could lower the relative risk of heatwaves on heat-related ED visits by 25-50%, the corresponding maximum medical cost could be reduced by .$384-$686 million.

This study underscores the urgent need for proactive policies to protect NYC residents from the increasing threat of heatwaves. By integrating climate resilience strategies into urban planning, public-health initiatives, and insurance frameworks, policymakers can work toward reducing the human and economic costs of extreme heat events while ensuring long-term sustainability and public safety.

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