A fourteen-year analysis of thermal stress in Kuwait.

The Arabian Peninsula region, particularly the Gulf Cooperative Countries (GCC) experience extreme heat with a warming trend and frequent and intense heat waves. Summer maximum temperatures (June, July, and August 'JJA') routinely soar above 50 °C. In this study, we analyzed the heat index (HI) for every hour of the last 14 years (2012-2025) in Kuwait. Heat Index is the combined metric incorporating ambient air temperature and relative humidity (RH) - or the ''feels like'' temperature. Specifically, we used the US National Weather Service (NWS) HI and classified three risk-threshold systems: HI classified according to Kuwait Oil Company "KOC thresholds", HI classified according to Saudi Arabia Aramco "Aramco thresholds", and HI classified according to the NWS "NWS thresholds". We divided hours and days into four HI category ranges (Extreme Danger, Danger, Extreme Caution, and Caution). Results show a positive linear trend for the annual minimum, average, and maximum temperature and RH during the study period. The mean annual numbers of days of 'Maximum' HI levels in the 'Danger' category were (119.71 (32%), 96.78 (26.51%), 101.64 (27.84%)) for KOC, Aramco, and NWS thresholds, respectively. The total annual number of days of 'Maximum' HI levels exceeded the 'Extreme Danger' category for KOC (≥ 46 °C), Aramco (≥ 52 °C), and NWS (≥ 54 °C) by 282 days (77%), 29 (7.9%), and 5 days (1.36%), respectively. The year 2025 demonstrated the highest number of days on which daily maximum HI exceeded the 'Extreme Danger', particularly in August. A total of 17 h exceeded the NWS threshold (≥ 54 °C), and the hours ranged from as early as 9 am to 4 pm. Moreover, HI as high as 52 °C was observed, in some instances, as early as 7 am and as late as 7 pm and midnight. This study provides a basis for heat stress extremities in hot arid environments, especially in the era of climate change. Temporal variability in thermal stress is essential to understand for both public and occupational health.