In January 2026, scientists from the India Meteorological Department and the Indian Institute of Tropical Meteorology in Pune dug into what’s behind humid heatwaves intensifying across India. These heatwaves keep showing up more often and are only getting stronger, which is a growing risk for public health and how we’re going to handle the changing climate. The research points out that it’s not just local weather, but far-off atmospheric shifts and warming oceans nearby, teaming up to make these humid heatwaves even worse across India.

What Are Moist Heatwaves and Why Are They More Dangerous?

There are two types of summer heatwaves in India: dry heatwaves and moist heatwaves. While dry heatwaves are limited to the northwestern plains and have not shown a significant increasing trend, the trend in moist heatwaves is increasing significantly. In this kind of heatwave, the humidity is high, and the sweat does not evaporate, making it difficult to cool the body.

Key characteristics of moist heatwaves:

• Humidity-driven heat stress: An increase in humidity levels, in addition to a rise in temperature, causes the body’s natural cooling system to shut down, leading to severe heat stress and heatstroke.
• Accelerating trend: Researchers have observed a statistically significant increase in the number of humid heatwaves in India in the past decades.
• Rising heat stress levels: According to a study, the levels of moist heat stress in the country have risen by nearly 30%, covering a wider geographical area in the past 40 years.
• Large population at risk: In the Indian subcontinent, there are over 1 billion people exposed to severe humidity-driven heat conditions, particularly farmers, laborers, and the elderly.

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How Do Atmospheric Waves from Europe Trigger These Heatwaves?

Many of the humid heatwaves in India are caused by large atmospheric disturbances, called Rossby waves, originating from near Europe’s west coast, which can travel thousands of kilometers to the Middle East and the Indian Ocean before reaching India.

Mechanism Behind the Intensification

• Rossby wave propagation: Atmospheric waves propagating from Europe generate high-pressure systems in the upper atmosphere over India, inhibiting cloud formation and holding in heat.
• Bay of Bengal: Anomalous surface temperature increases in the southern Bay of Bengal generate circulating wind patterns that reinforce high-pressure systems over India.
• Amplification: When the two systems arrive together, they overlay each other, thereby increasing the strength of the anti-cyclonic system and prolonging the heat event.
• Confirming the mechanism: The mechanism has been confirmed by scientists via 129 atmospheric model simulations.

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What Does This Mean for India’s Future Climate Risks?

The research has shown that the combination of waves in the atmosphere and the warming of the ocean waters could make the occurrence of humid heatwaves more intense in different parts of India. However, if the Rossby waves change their pattern even slightly, the areas that could be exposed to the greatest heat stress could be shifted from the northwest of the country to the east and southeast coastal areas of India.

In the face of rising temperatures globally, climate change models predict that the occurrence of oppressive heatwaves, which are associated with high temperatures and humidity, could rise many times over by the end of the century. As such, climate monitoring and forecasting would be key in addressing the humid heatwaves intensifying across India as an environmental and health challenge.

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