The Bangkok Metropolitan Administration's (BMA) Environment Department, which publishes a daily heat-index forecast, said the June 25 reading fell within the "danger" category, defined as 42 to 51.9 C.
The Nation reported that officials urged residents to cut outdoor activity between 11 a.m. and 3 p.m. and to watch for symptoms of heat illness.
The actual air temperature was far lower. The Thai Meteorological Department forecast highs of about 34 to 39 C with a 20% chance of afternoon thunderstorms, Bangkok Post reported.
The difference is humidity. The heat index, often labeled the "feels like" temperature, combines air temperature with relative humidity.
When the air is saturated, sweat evaporates slowly and the body struggles to shed heat. Air in the mid-30s C can feel like the high 40s once humidity climbs.
