<b>Heat Stress Metrics for US Census Tracts 1998-2020 [DATASET]</b>

<b>Abstract: </b>Extreme heat exposure is a growing public health threat. Heat-health research has commonly used dry-bulb temperature to characterize heat exposure, partly due to limited availability of spatially explicit, public-health-aligned datasets that integrate multiple meteorological factors to quantify heat stress. We address this gap by providing hourly Heat Index (HI), Wet-Bulb Globe Temperature (WBGT), and Universal Thermal Climate Index (UTCI) for U.S. Census tract boundaries across the contiguous United States from 1998–2020. Heat-stress fields were generated by integrating PRISM, ERA5-Land, and National Solar Radiation Database (NSRDB) products, with near-surface temperature and moisture fields reconstructed and ancillary variables interpolated to a harmonized 800-m grid. Heat-stress indices were computed using validated physical models and aggregated to census tracts using area- and population-weighted methods. Validation against station networks shows stable performance for sample year 2010 May-September, with air-temperature RMSE of 1.70 °C, Heat Index RMSE of 3.20 °C, WBGT RMSE of 2.90 °C, and UTCI RMSE of 3.26 °C. These tract-level hourly heat-stress datasets enable direct linkage with public health data.<b>Data Records and Use:</b> We developed an open-access dataset of area-weighted and population-weighted, hourly heat exposure estimates aggregated to U.S. Census Tract boundaries across the contiguous United States. The datasets are stored in parquet format and each file represents two half UTC days and is stored in the following format: <i>heatstress_tract_area_and_popweighted_[DATE]_[DATE + 1]_popy[Population YEAR]_v[Vintage Year].parque</i>t, with total storage of all files around 515GB. Specifically, each Parquet file corresponds to a single PRISM day and contains tract-level hourly heat stress estimates spanning a 24-hour UTC exposure window from 12:00 UTC on the previous calendar day to 11:00 UTC on the labeled day. This convention maintains temporal consistency between daily PRISM products and the sub-daily meteorological inputs used in heat stress modeling while avoiding ambiguities associated with calendar-day aggregation. A complete description of the census-tract parquet file structure, including variable names, units, and definitions, is provided below:<br>GEOID: Census tract identifier (NHGIS-compatible)year: Year of observation (UTC-based)month: Month of observation (UTC-based)day: Day of observation (UTC-based)time (hour): Hour of day (0–23, UTC-based)temp_C_used_area (°C): Area-weighted tract mean air temperaturetemp_C_used_pop (°C): Population-weighted tract mean air temperaturerh_pct_used_area (%): Area-weighted tract mean relative humidityrh_pct_used_pop (%): Population-weighted tract mean relative humidityHI_C_area (°C): Area-weighted Heat IndexHI_C_pop (°C): Population-weighted Heat IndexWBGT_C_area (°C): Area-weighted Wet Bulb Globe TemperatureWBGT_C_pop (°C): Population-weighted Wet Bulb Globe TemperatureUTCI_C_area (°C): Area-weighted Universal Thermal Climate IndexUTCI_C_pop (°C): Population-weighted Universal Thermal Climate Index<b>Notes:</b> Daily Parquet files are stored in year ZIP folders on figshare. Parquet day files are missing for 2002-01-15, 2002-01-16, 2007-10-10, 2007-10-11, 2007-11-03, and 2007-11-04 due to missing input data.