India is bracing for a colder-than-usual winter, as the India Meteorological Department (IMD) forecasts an increase in cold wave days across parts of central, north-west, and north-east India. The unusual chill is attributed to the combined influence of the polar vortex and La Niña conditions, which are expected to drive temperatures down across these regions.
Spatial forecasts indicate that Haryana, Rajasthan, Delhi, and Gujarat are likely to experience below-normal temperatures during the winter months. The IMD predicts that between one and four, or possibly more, cold wave days could occur in these areas from December through February, compared to the usual five to six days typically recorded in north-west India over this period.
A cold wave is officially declared when the minimum temperature falls below roughly 90% of the daily recorded temperatures and drops below 15°C, persisting for at least three consecutive days.
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Across most of central India, adjoining peninsular regions, and north-west India, minimum temperatures are expected to range from normal to below normal. Conversely, other parts of the country are likely to see above-normal minimum temperatures. In December specifically, minimum temperatures are forecast to be normal to below normal over central and north-west India, as well as the northern parts of peninsular India. Meanwhile, daytime maximum temperatures are predicted to remain above normal across most regions, except central India and adjacent north-western and peninsular areas, where they are expected to be normal to slightly below average.
The IMD also expects December rainfall across the country to remain largely within the normal range of 79-121% of the long-period average. Peninsular India and west-central regions, along with parts of east-central and north-east India, are forecast to receive above-normal rainfall, while most other areas are likely to record below-average precipitation.
Understanding Polar Vortex And La Niña Impact
The cold conditions are closely linked to the polar vortex, a large low-pressure system of frigid air surrounding the Earth’s poles, which strengthens during winter. The IMD notes that the polar vortex influenced temperatures over north-west and central India in November, resulting in below-normal conditions, and is expected to continue exerting an impact over the coming months.
“Below-normal temperatures and cold wave conditions over Madhya Pradesh were influenced by the polar vortex and La Niña conditions. Now, the polar vortex is once again affecting the region,” said OP Sreejith, scientist and head of the Climate Monitoring and Prediction Group at the IMD.
La Niña, which involves large-scale cooling of ocean surface temperatures in the central and eastern equatorial Pacific, alters atmospheric circulation patterns, including winds, pressure, and rainfall. Typically, it brings opposite climate impacts to those of El Niño, often resulting in harsher winters in India. The IMD expects La Niña to persist through the Northern Hemisphere winter, with a likely transition to ENSO-neutral conditions between January and March 2026, with a 61% probability.
M Mohapatra, Director General of the IMD, added, “The forecast is based on a dynamical system. Not many western disturbances are expected this winter, and La Niña will continue to play a significant role in influencing temperatures.”
Recent Weather Trends
November saw minimum temperatures across most of India at normal to below normal levels, except for many parts of the north-east and peninsular regions. Rainfall was significantly below average nationwide, with a 42.8% deficit recorded. North-west India experienced the highest shortfall at 78.1%, followed by central India at 51.3% and the south peninsula at 43.6%. Conversely, east and north-east India saw an 8.9% excess in rainfall.
As India heads into winter, residents across the affected regions are advised to prepare for colder-than-usual conditions and take necessary precautions during cold wave events.
