Temperatures across India have started decreasing with the start of the winter season, which officially runs from December to February. However, an HT analysis shows that the season has been unusually warm compared to winter seasons so far by minimum temperatures. While the reason for this warm beginning to winter is unseasonal rain in parts of the country due to Cyclone Michaung, a strong El Niño prevailing currently means that this warming is likely to continue. Here are four charts
- India’s average minimum temperature up to December 12 is 14.8 °C. This is 2.3 °C warmer than the 1981-2010 average, considered normal temperature in India. This has made the first twelve days of the 2023-24 winter the second warmest since 1951, the first year for which the India Meteorological Department (IMD) has published gridded data for temperature. To be sure, this warming in minimum temperatures has decreased in the past three days. The first nine days of the month were all at least 2 °C warmer than normal. The last three days have only been 1.2 °C, 0.5 °C, and 0.7 °C warmer than normal. A similar gradual cooling also happened in the warmest December month on record (2019) in India. The first 12 days of December 2019 were 3.2 °C warmer than normal on average. However, the month ended up only 2.8 °C warmer than normal. To be sure, the trend in maximum temperatures is opposite to that of minimum temperatures so far. India’s average maximum up to December 11 (December 12’s maximum temperatures will only be available on December 13) is 25.6 °C, 0.95 °C cooler than normal and the ninth coolest since 1951.
- State-wise averages of minimum temperatures show that of the 30 states and union territories (UTs) for which this calculation is possible, only Jammu & Kashmir and Ladakh have experienced a cooler than normal start to winter. However, a warming in the rest of the country does not mean that they are all experiencing a similar departure from normal. The minimum in Madhya Pradesh and Bihar is around six degrees warmer than normal. This trend of high warming is reflected across states in eastern and central India. On the other hand, north-western states such as Rajasthan, Punjab, Haryana, and the UT of Delhi are only 2.5-3 °C warmer than normal and the hilly states of Himachal Pradesh, Nagaland, and Sikkim are less than a degree warmer than normal. A week-wise breakup further shows that the warming has decreased in 21 of 30 states and UTs in the second week of the month, with only southern and northeastern states becoming warmer.
- One reason why minimum temperatures were much warmer than normal in eastern and central states in the first week of December is the unseasonal rain brought by Cyclone Michaung. Rain tends to increase minimum temperatures because clouds trap outgoing heat at night when minimums are recorded. This seems to have played a role in a warm beginning to winter. While southern states such as Tamil Nadu, Karnataka, Kerala, and parts of Andhra Pradesh and Telangana do receive rain in December due to the northeast monsoon (this season runs from October to December), other states usually don’t. However, all big states except Karnataka received surplus rain in the first week of December this year. As is expected, Andhra Pradesh – where Michaung’s landfall happened – received the most rain in absolute terms in the first week of December: 139 mm. Similarly, there was unusually high rainfall along individual places on the east coast. For example, according to IMD’s gridded dataset, Chennai and neighbouring districts (Thiruvallur and Kancheepuram) received 151 mm of rain in the 24 hours ending 8:30 AM on December 4. This is the 19th highest daily rain for any day since January 1, 1901, for these three contiguous districts.
- While warming in minimum temperatures has decreased after Cyclone Michaung, current IMD forecasts show warming in the northern half of the country again in the last week of December. In fact, IMD has forecast a warmer than normal winter as a whole. One big reason for this is the prevailing El Niño situation, which increases global temperatures. El Niño is the periodic warming of the equatorial Pacific Ocean and has been intensifying almost continuously this year. In the week ending May 31, sea surface temperatures in the Nino 3.4 region (a part of the Pacific Ocean monitored for El Niño trends) were 0.8 °C warmer than normal. This warming reached a high of 2.1 °C in the week ending November 22 and was 1.9 °C in the week ending December 6. Since most models predict this warming to remain above the threshold of 0.5 °C up to the April-June season, its warming effect is likely to be active the entire 2023-24 winter season.
Abhishek Jha is Assistant Editor-Data at Hindustan Times. He uses statistical programming to generate newsworthy insights from large datasets. He is part of the team that produces Number Theory, a daily data story feature of the paper’s print edition. Since March 2024, he has been writing Weather Bee, a weekly column for the Hindustan Times website. He is a chemical engineer by training, who specialises in stories related to weather, climate, and the environment. Jha has been at HT since 2018, where he offers data-driven perspective and analysis on politics, environment, weather, climate, economy and society. His work includes data coverage of elections in India and abroad, including the 2019 and 2024 Lok Sabha elections; the disasters and extreme weather resulting from changing climate, such as floods, droughts, heat waves, cold waves, and dwindling snow cap in the Himalayas; the factors that drive poor air quality in northern India; the changing patterns of land use; the Covid-19 pandemic and its impact on labour market conditions; the changing pattern of consumer spending seen in the new consumer spending surveys; and social norms seen in the surveys such as the National Family Health Survey.