If you are from Delhi or even Northern India, chances are high that you would have wondered what’s with these unusual weather fluctuations? It’s May 1 and the minimum temperature in Delhi was 19.6° Celsius. The lowest ever temperature recorded in May in Delhi stands at 15.2° Celsius on May 2, 1969. As Delhites woke up to this record-breaking low temperatures of recent years for the month of May, let’s look at what has kept Delhi’s weather so unpredictable in the last few months.

January, this year, witnessed one of the coldest temperatures of recent years at 6.6 degree celsius while February was the warmest with a mean maximum temperature of 27.7 degree celsius. April also ended on a cooler-than-usual note with the maximum temperature settling at 28.7 degrees Celsius, on April 30. This was 10 degrees below the normal for this time of the year. Though there is still no conclusive evidence around whether these fluctuations could be attributed to climate change yet it’s a possibility that can’t be ignored in the long run.

So what exactly led to such unpredictable weather changes in Delhi? 

As for the unseasonal downpour, the main reason was attributed to “Western Disturbances” as per the Indian Meteorological Department (IMD). The IMD has in fact issued a rain alert for the next five days with a warning of heavy rainfall in the Western Himalayan region (more than 6.5 cm of rainfall). The IMD forecast has also said that snowfall is likely to occur at many places over 3,500 metres in the Northern state of Uttarakhand. 

At present, there are multiple cyclonic circulations and low-pressure belts that are leading to rains across large parts of the country. There is a cyclonic circulation induced by a western disturbance that is lying over south Pakistan and adjoining West Rajasthan, a cyclonic circulation is lying over southwest Uttar Pradesh and another over south Chhattisgarh, and a trough/wind discontinuity is running from east Vidarbha to north-interior Tamil Nadu.

Western disturbances are responsible for nearly 5% to 10% of India’s annual rainfall, making them a crucial source of precipitation for the country. Western Disturbances refer to the westward moving low-pressure systems that originate close to the Mediterranean region. These disturbances usually bring in cool and moist winds that collide with the Himalayas, leading to snow and rainfall in the northwestern regions of the Indian subcontinent, impacting other countries such as Pakistan, Bangladesh, and Nepal as well. 

One of the reasons for the abnormally hot February (hottest since 1901) was the formation of a high pressure area near the land surface, which caused the air to descend, compress and heat up. Western Disturbances, avoiding its typical path during winters, have started visiting India more frequently during the summers because of the warming in the Arctic region. According to reports this leads to subtropical westerly jet streams that move downwards in the summers.

This uncharacteristically cooler start to the summer, which is likely to persist for a few more weeks in several parts of the country, may hurt the arrival of the crucial monsoon season at a time when the rainy season is expected to anyway be sapped by the Pacific warming phenomenon El Nino

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