Sometimes missing the heat: the risk of underestimating extreme heat days with daily maximum heat index approximation.

ABSTRACT: The heat index (HI) metric is used in many studies linking weather conditions (observed or climate model-projected temperature and humidity) to health impacts. Because climate models often provide only daily data, a common approximation method estimates the daily maximum HI (hismaxest) from daily maximum temperature (tasmax) and minimum relative humidity (hursmin), assuming they coincide with the actual peak HI (hismax24). This study evaluates the accuracy of this approximation using hourly station-based data from NOAA's Integrated Surface Database (ISD-Lite) and the U.S. Climate Reference Network (USCRN). Though we find that hismaxest either matches or slightly underestimates hismax24 for most summer days and locations, it significantly underestimates the occurrence of extreme heat days i

SUBMITTER: Xu WR 

PROVIDER: S-EPMC12540600 | biostudies-literature | 2025 Nov

REPOSITORIES: biostudies-literature