Forecasters could give India weeks of advance warning before moist heatwaves strike, allowing cricket matches and major gatherings to be rescheduled and reducing the risk of heat exhaustion and death.
Scientists have shown for the first time that India's summer monsoon actively controls the location and timing of moist heatwaves across the country. The findings reveal a striking regional pattern that forecasters could use to predict these events days or weeks ahead.
Unlike ordinary heatwaves, moist heatwaves are driven by humidity as much as temperature. When air is already humid, sweat cannot evaporate from skin, leaving the body unable to cool itself. This can lead to heat exhaustion and fatal heatstroke within hours.
Scientists from the University of Reading studied more than 80 years of weather data and found that, depending on whether the monsoon is active or running dry, the region of greatest risk can shift dramatically from one part of the country to another. The research is published in the journal Climate Dynamics .
Dr Akshay Deoras, who led the study, said: "We often find people being more aware of dry heatwaves in India given the scorching summer season, but moist heat remains less known and is therefore more dangerous. Outdoor public gatherings are notorious for causing heat exhaustion. Advance warning of a moist heatwave could allow organisers of public events, such as cricket matches and other large gatherings, to reschedule activities, extend drinks breaks, and strengthen on-site medical provision to protect both participants and spectators.”
"Our research shows for the first time that the monsoon is the key driver of where and when this deadly risk develops. Because we can forecast these monsoon patterns weeks ahead, this creates real opportunities to prepare and protect people.
“Advance warnings could also allow hospitals to increase staffing before moist heat-related admissions rise, enable city authorities to open cooling centres and adjust school hours, and help power grid operators manage infrastructure strain.”
Monsoon rains shift moist heatwave risk across India
When the monsoon brings heavy rain, northern India faces the risk of moist heat. As the rain subsides during dry spells, this danger shifts to the southern and eastern parts of the country. This happens because northern India is normally dry, so monsoon moisture pushes humidity to dangerous levels. In the south and east, humidity is already high, so dry spells and clear sky conditions trap heat instead.
Humidity matters more than temperature in making these conditions deadly. It is often the moisture in the air, not the number on a thermometer, that can cause moist heat related deaths. Over a billion people in India face this threat, particularly agricultural workers, labourers and elderly people.
Crucially, the study links moist heatwaves to a large-scale weather pattern that can be forecast two to four weeks ahead. During one specific phase of this large-scale weather pattern, heatwave occurrence over northern India rises by 125% above normal. Forecasters could use these patterns as early warning signs and save lives.
Climate Dynamics
Anatomy of moist heatwaves in India during the summer monsoon season
16-Feb-2026