Academic warns heat index, not temperature, drives heat-stroke risk in Thailand
Environmental health academic Dr Sonthi Kotchawat urges the public to watch the heat index as humidity can push “feels like” temperatures into dangerous ranges, raising heat-stroke risk even when thermometers look manageable.
Thailand’s hot season is getting under way, and an environmental and health academic has warned that the danger of extreme heat should not be judged by thermometer readings alone, urging people to monitor the heat index—a measure more closely tied to heat illness and heat stroke.
Dr Sonthi Kotchawat said on Facebook that high humidity can sharply raise the “feels like” temperature, increasing health risks even when the air temperature appears only moderately high.
Heat index explains what the body actually feels
Dr Sonthi explained that the heat index reflects the temperature the human body “actually feels” at a given moment, calculated using air temperature and relative humidity.
He noted that during Thailand’s summer months—typically March to mid-May—relative humidity often averages 60–75%. Under those conditions, a thermometer reading of 36°C can translate into a heat index above 50°C, which he described as extremely dangerous.
Why humidity makes heat more dangerous
According to the academic, the body cools itself mainly through sweating—but humidity changes how well that works. When humidity is low, sweat evaporates more easily and the body can release heat more effectively. When humidity is high, sweat evaporates poorly, causing heat to build up in the body and increasing the risk of heat-related illness.
Heat index risk levels linked to heat stroke
Thailand’s risk guidance for heat index is commonly grouped into escalating tiers: 27–32°C (caution/watch), 32–41°C (extreme caution), 41–54°C (danger), and 54°C and above (extreme danger)—with the highest levels carrying a significant risk of heat stroke.
Practical steps the public is urged to take
Dr Sonthi advised people to adjust behaviour when the heat index rises—such as drinking 2–3 litres of water a day (sip regularly before feeling thirsty), wearing light-coloured, loose-fitting clothing, cooling the body when overheated, and avoiding strenuous outdoor activity—especially between 11.00am and 3.00pm.
