Brace for longer heatwaves and floods

In May 2024, Churu in Rajasthan scorched at 50.5°C, as large parts of India were gripped by an intense heatwave.

At least 37 cities across the country endured temperatures above 45°C, affecting life, livelihoods, and water resources across India. Parts of Maharashtra were compelled to ban public gatherings due to the extreme heat. This year, the India Meteorological Department (IMD) has again forecast above-normal maximum and minimum temperatures over April to June, with longer heatwaves across the country.

Parts of western India are projected to experience 7-8 additional days under heatwave conditions this summer.

Yet, in what may appear paradoxical at first glance, the IMD’s Long Range Forecast (LRF) has predicted an above-average Southwest Monsoon, anticipating around 5% more rainfall than the (long-period) average. Most importantly, in recent years, surplus rainfall has often been accompanied by extreme rain events that cause floods.

How do we understand this forecast of above-normal summer heat followed by above-average rainfall?

Several interconnected meteorological and climatic phenomena underpin these predictions.

A warming world

The World Meteorological Organization has confirmed 2024 as not just the warmest year on record, but also the first calendar year that saw a global mean temperature of more than 1.5°C above the 1850-1900 average.

This is, of course, the manifestation of human-caused global warming. That warmth has rolled into early 2025, manifesting in India in the occurrence of heat waves and warm nights as early as February/March.

The early warmth in 2025 is a continuation of India’s long-term warming trend, with the land temperature average having risen by nearly 0.8°C since the beginning of the 20th century. Surface and atmospheric warming doesn’t just elevate baseline summer temperatures. It also increases the atmosphere’s moisture carrying capacity. This additional moisture, together with changing circulation patterns, prime the monsoon for intense and erratic downpours.

The current ocean-atmosphere state

The El Niño–Southern Oscillation (ENSO) is a climate pattern involving temperature changes in the equatorial Pacific Ocean that affects global weather.

The year began with a weak La Niña (cooler ocean temperatures over central and eastern Pacific) but ocean-surface temperatures have since normalised. Although the atmosphere still shows a residual La Niña-type convection in the western Pacific, ENSO-neutral conditions are favoured over the next few months, and expected to persist through to October. The absence of El Niño conditions in the tropical Pacific is expected to facilitate normal moisture inflow and convection during the monsoon season.

Additionally, the ‘Indian Ocean Dipole’ (IOD) — a measure of temperature differences across the Indian Ocean — is also neutral this year; therefore, neither suppressing nor enhancing monsoon activity.

The neutral state of both these major climate drivers create conditions where other factors can exert a greater influence on the monsoon system.

Lower Eurasian snow cover

Snow cover across Eurasia from January to March was markedly below normal, with serious deficits in the Hindu Kush Himalayas and the Tibetan Plateau. Arctic Sea ice extent in March has ranked lowest on record (for March) since satellite observations started in 1979.

Snowpack plays an important role in planetary energy balance by influencing land surface reflectivity. Lower snow cover leads to reduced land reflectivity, which increases its absorption of solar energy.

Reduced winter–spring snow cover over western and central Eurasia leaves a darker, drier land surface in April-May.

Since less incoming solar radiation is diverted to snowmelt and evaporation, the Eurasian landmass warms more rapidly.

The resulting stronger continental-ocean and meridional tropospheric temperature gradients intensify the low-level south-westerlies, raising the odds of above-normal Indian summer monsoon rainfall, especially when ENSO and the IOD remain neutral. A cautionary note is warranted. It has been recently suggested that the inverse relationship between central Eurasian spring snow cover with the Indian summer monsoon is weakening due to global warming.

The forecast explained

India’s 2025 outlook is a textbook study in how short-term drivers of weather stack atop long-term warming: Baseline warming sets the global average context by loading the dice for a warmer summer and a moister monsoon, and lower winter/spring snow cover in western Eurasia, the Himalayas, and the Tibetan plateau is expected to promote higher land surface warming, which could strengthen the monsoon circulation leading to increased rainfall during the monsoon.

Other large-scale phenomena and weather systems such as the Madden–Julian Oscillation (a wave-like movement of rain clouds around the tropics, particularly the Indian and Pacific Oceans ), North Atlantic Oscillation (a shifting pattern of atmospheric pressure over the North Atlantic), depressions, and cyclones can exert significant influence on the date of onset and the wet-dry pattern of the monsoon.

Moreover, above-normal rainfall on paper may still arrive as alternating deluge and lull; the benefits and impacts of the monsoon will be shaped by these patterns.

Preparedness hinges on real-time monitoring.

(Chirag Dhara is a climate and sustainability scientist at Krea University, India.)

(Ayantika D C is a climate scientist at the Indian Institute of Tropical Meteorology, Ministry of Earth Science, India.)

This article was first published under Creative Commons by 360info.

Disclaimer: The views expressed above are the authors' own. They do not necessarily reflect the views of DH.