Challenges and Opportunities in Estimating the Mortality Burden Related to Heat Exposure: Maricopa County, Arizona,...

Objectives. To estimate the mortality burden attributable to daily mean temperatures during the heat season (April through October) in Maricopa County, Arizona. Methods. We examined the effects of heat exposure on 126 854 deaths that occurred in Maricopa County during the 2019 to 2023 heat seasons. Using a quasi-Poisson regression with distributed lag nonlinear models, we estimated the cumulative relative risk (relative to 77°F) between population-weighted daily mean temperatures and all-cause mortality over a lag period of 3 days. Results. At 99°F (the 95th percentile of the population-weighted daily mean temperature), we observed an 11% (95% confidence interval [CI] = 7%, 16%) increase in daily all-cause mortality relative to 77°F. Overall, 3036 (95% empirical CI = 968, 4887) deaths were attributable to heat, which is 57% more deaths than identified through epidemiological heat surveillance. Conclusions. The mortality burden increases with increasing population-weighted daily mean temperatures, indicating that the effects of heat on mortality can be indirect and incompletely captured by routine surveillance. Public Health Implications. Statistical approaches can help estimate the mortality burden associated with heat exposure, complementing countywide surveillance efforts that provide actionable insights into enhancing heat prevention strategies. (Am J Public Health. 2026;116(6):810-813. https://doi.org/10.2105/AJPH.2026.308443).