IMD warns of wet‑bulb danger
- India’s weather office said heat-wave conditions would persist across isolated pockets of northwest and central India on April 27 before easing after that. - The India Meteorological Department also warned of hot, humid conditions in coastal states and a 3-5°C fall in northwest temperatures from April 28. - Wet-bulb heat matters because humidity blocks sweat from cooling the body. (mausam.imd.gov.in)
Wet-bulb temperature is heat plus humidity: a measure of how hard it is for sweat to cool the body. When that number rises, people can overheat even when the air temperature alone does not look extreme. (mausam.imd.gov.in) (pmc.ncbi.nlm.nih.gov) The India Meteorological Department said on April 27 that heat-wave conditions were likely to persist over isolated to scattered pockets of northwest and central India that day. Its all-India bulletin dated April 26 had warned the same regions could see heat-wave conditions for the next three days. (mausam.imd.gov.in 1) (mausam.imd.gov.in 2) The same bulletin said maximum temperatures over northwest India were expected to show no significant change through April 27, then fall by 3-5 degrees Celsius from April 28 to May 1. It also warned of hot and humid weather in isolated pockets of Konkan, Kerala, coastal Gujarat, Tamil Nadu and Odisha. (mausam.imd.gov.in) That distinction matters because the body cools itself by evaporating sweat, and humid air slows that evaporation. In extremely hot and humid conditions, the body can heat up faster than it can shed heat. (cdc.gov) (weather.gov) For years, 35 degrees Celsius wet-bulb was treated as a rough upper survival limit for humans, but newer lab research found the practical limit for young, healthy adults can be closer to 31 degrees Celsius in saturated air. Older people and people with illness are more vulnerable at lower levels. (psu.edu) (nature.com) India’s public-health guidance lists older adults, infants, pregnant women, outdoor workers, and people with heart disease or high blood pressure among groups at higher risk during heat waves. The advisory tells employers and local officials to provide water, shade, schedule changes and temperature displays at workplaces. (ncdc.mohfw.gov.in) Heat stroke is the most severe heat illness, and U.S. and Indian health guidance describe the same red flags: confusion, fainting, seizures, very high body temperature, and skin that may be hot with reduced sweating. The National Institute for Occupational Safety and Health says body temperature can rise to 106 degrees Fahrenheit, or about 41.1 degrees Celsius, within 10 to 15 minutes. (cdc.gov) (mayo.edu) (osha.gov) Climate and health researchers have also warned that humid heat extremes are increasing, with serious effects well below the theoretical survival threshold. The Lancet Countdown’s India data sheet says rising heat exposure is already driving illness, deaths and labor losses. (pmc.ncbi.nlm.nih.gov) (lancetcountdown.org) The immediate message from India’s late-April forecasts was simple: a dry thermometer does not tell the whole story. In a heat wave, humidity can turn a bad day into a medical emergency much faster. (mausam.imd.gov.in) (cdc.gov)
