Why Delhi was unusually warm this winter? Here're the reasons for rising temperature

January 2025 set records as the warmest January in eight years, and February has continued to show elevated temperatures

The winter season is nearing its closure in New Delhi, and the skies have become clearer. However, the city, which is famous for cold waves during winter, has experienced an unusually warm spell, with temperatures significantly higher than normal. The typical chill that Delhiites expect during the colder months has been notably absent this season.

October 2024 saw the highest temperatures in 73 years, and November was the warmest in eight years. December followed suit with above-average temperatures in the first half of the month. January 2025 also set records as the warmest January in eight years, and February has continued to show elevated temperatures, with a high of 29.7 degrees Celsius recorded on February 13, six degrees above the usual norm for this time of year, according to the India Meteorological Department (IMD).

This winter season has witnessed the absence of cold waves, which are typically a defining feature of Delhi winters. In December, only a single cold wave day was recorded, and that was the only cold wave event throughout the entire season. Safdarjung, the city's base weather station, did not register any cold wave days, although some isolated areas of Delhi experienced "cold wave day" conditions.

What is ‘Cold Wave Day’?

A "cold wave day" is declared when the maximum temperature is significantly lower than usual, but cold wave conditions, which are defined by a much lower minimum temperature, were virtually non-existent this season. According to the IMD, this unusual warmth in Delhi and across northwest India is mainly due to weak or feeble western disturbances, which are typically responsible for causing temperature dips during winter months.

What led to the warmth?

Mrutyunjay Mohapatra, the director general of the IMD, told the reporters that this warmer-than-usual winter can be attributed to the absence of robust western disturbances. “These disturbances are weather systems that generally cause temperature drops in the region, bringing cold air from the northwest and leading to cold wave conditions,” he explained.

However, the disturbances this season were much weaker than usual, resulting in a lack of rainfall and snowfall in the Himalayan region, which further contributed to the warmer temperatures. The overall weather patterns for the season were also impacted by these feeble western disturbances, leading to a general rise in temperatures throughout the region.

In the absence of consistent northwesterly winds that normally bring cold air from the mountains, Delhi experienced clear skies for much of the winter. This allowed solar radiation to reach the surface and raise the temperatures. Normally, clouds and rain can act as a shield, preventing the sun’s heat from directly warming the ground, but this winter, rain was sparse, exacerbating the overall warmth.

Among the several factors that have contributed to this warmer-than-usual winter, one is the absence of La Niña conditions, which were expected to develop in December but did not materialise. La Niña typically brings colder conditions to north India, so its absence has likely contributed to the milder winter temperatures.

Low Rainfall

According to IMD data, the rainfall during October and November was extremely low, with a 100% deficit in both months. December did bring some relief in the form of rainfall, with 53.8 mm recorded over the course of the month, making it the wettest December in 27 years. However, this rainfall was largely concentrated in one day—December 28—when 41.2 mm fell, marking the highest daily rainfall in the city in 101 years. While the rain did lower temperatures temporarily, especially on December 28, it was not enough to sustain long-term cooling effects.

January, in contrast, experienced a rainfall deficit again, recording just 6.6 mm against the expected 19.1 mm, resulting in a 65% shortfall. Notably, January 2025 did not witness any cold wave or cold day events, in stark contrast to January 2024, when five cold days and five cold wave days were recorded. The absence of these events contributed significantly to the unseasonably warm temperatures.

February, which is typically one of the coldest months of the year in Delhi, has also been uncharacteristically warm. Only 0.5 mm of rainfall was recorded on February 4, and temperatures throughout the month have generally remained above normal, further prolonging the unseasonable warmth.

This winter is a stark contrast to the previous year, when Delhi recorded five cold days and five cold wave days—the highest number since 2012-2013. In 2024, the lowest temperature recorded was 4.5°C, which, while cold, was still the highest minimum temperature in 15 years for the city.