El Nino cycles can help predict dangerous humid heat and lost work hours months in advance

Outdoor workers across India face severe health risks and falling work output as extreme humid heat stretches long into the night, according to a recent scientific study. Manoj Borah, a welfare officer at a tea garden in Kamrup district, Assam, says high nighttime temperatures prevent workers from resting properly. Tea gardens and agricultural fields in the region have adjusted outdoor work hours to start at 5 AM and end by noon. India accounts for more than half of the global rise in potential productivity loss from extreme humid heat since the mid-1980s, based on findings published in the Journal of Geophysical Research Atmospheres. Subodh Kumar Saha, a scientist at the Indian Institute of Tropical Meteorology in Pune and the paper's corresponding author, warns that continued exposure during extreme humid heat can cause heat stroke and death. Humid heat combines high temperatures and high moisture, creating a wet-bulb temperature where the body cannot cool down through sweat evaporation. When wet-bulb readings exceed 33 degrees Celsius, the condition becomes dangerous to human health, while heart and kidneys suffer slow damage over time.

Early Warning

Researchers discovered that swings in productivity losses track closely with the El Nino-Southern Oscillation, a natural cycle of Pacific Ocean warming and cooling. Because this weather pattern evolves slowly, scientists can forecast humid heat stress one to six months ahead. This advance notice provides a vital window for water planning and climate-resilient farming. Professor B.N. Goswami of Gauhati University notes that heat stress events in the Northeast now last an average of 10 to 20 days, up from about five days in the 1940s and 1950s. Goswami stresses that India has good predictive models, but must better define heat conditions using local work data and communicate warnings clearly.

Context

Humid heat stress differs from dry heat waves because it can strike at any hour and often peaks well after daytime temperatures drop. Tracking large-scale climate cycles like El Nino allows researchers to connect seasonal shifts directly to human livelihoods and health. This early warning approach helps communities prepare for prolonged heat events that disrupt outdoor labor across vulnerable regions.