High-resolution WBGT-based assessment of urban heat stress in Dhaka, Bangladesh (2008–2017): Implications for Climate-Responsive Planning

• High-resolution WBGT maps reveal rising urban heat stress across Dhaka (2008–2017) • Occupational heat risk increased sharply in central and northern areas. • Extreme heat stress days (>32.2 °C) exceed 70 days/year in several urban zones. • Pre-monsoon and monsoon seasons show intensifying thermal stress conditions. Rapid urbanization and climate change are intensifying outdoor heat stress in tropical megacities, yet most urban heat assessments rely on air temperature or land surface temperature (LST) metrics that do not directly represent physiological thermal strain. This study presents a high-resolution (100 m) spatial characterization of heat stress in Dhaka, Bangladesh, using Wet Bulb Globe Temperature (WBGT) derived from the UrbClim urban climate model for 2008–2017. Daily minimum (WBGTmin), mean (WBGTmean), and maximum (WBGTmax) values were analyzed and classified according to internationally recognized occupational heat-stress thresholds. Results reveal substantial intra-urban variation in heat exposure, with central and northern wards—including Tejgaon, Motijheel, Mirpur, Pallabi, Uttara, and Kafrul—experiencing persistently elevated thermal risk. Monthly WBGTmax peaked in May (∼34.6 °C) and reached its minimum in January (∼22.2 °C), while WBGTmin was highest in July (∼26.9 °C) and lowest in January (∼13.9 °C), indicating pronounced seasonal contrasts in diurnal thermal exposure. WBGTmax exceeded the “extreme” occupational stress threshold (>32.2 °C) on 56 to 78 days annually in multiple wards during the pre-monsoon and monsoon seasons, with spatial patterns of exceedance showing strong consistency across years. Given the 10-year observational period, this study focuses primarily on characterizing persistent spatial patterns and seasonal dynamics of heat stress exposure rather than establishing long-term climatic trends. By applying a physiologically grounded heat-stress index at neighborhood scale, this research provides actionable spatial intelligence for climate-responsive urban planning, occupational safety regulation, and targeted heat-adaptation strategies in Dhaka and other rapidly growing tropical megacities.