North Indians have been witnessing unprecedented climate change. Lately, rainfall in many parts of the country has led to a significant drop in temperatures. While rains are not unusual, rains in the month of May are.

This time last year (in the first week of May), the minimum temperature in Delhi hovered around 22 to 28 degrees Celsius. However, this year, the minimum temperature touched 15 degrees Celsius, as per the data by the India Meteorological Department (IMD).

The maximum temperature in Delhi also remained between 28-32 degrees Celsius in 2023, while in the previous years, it hovered around 40 degrees Celsius.

On Thursday, Delhi's weather — from a foggy morning to a sultry afternoon — summarised the atypical patterns of the last 15 days and perplexed residents. The national capital saw the third coldest May morning since 1901 on Thursday, while it witnessed the second coldest May day in 13 years on Monday, as per PTI reports.

With more rain expected, the month of May, which is generally the hottest in Delhi, is likely to see fewer heatwave days, News 18 reported citing the IMD forecast.

So what has caused this unusual climate in Delhi and other areas of North India?

According to News 18, three very active back-to-back Western Disturbances hit the Himalayan region around April 27 and May 3. "These are the rainy systems that originate in the Mediterranean Sea and travel eastwards to bring rain/snow over India," the report said. These systems not only brought torrential rains to the hilly areas but even the plains for almost a week.

Some experts said such anomalous weather can be expected during the El Nino years — "a warming of the ocean surface, or above-average sea surface temperatures in the central and eastern tropical Pacific Ocean."

“El Nino year generally brings a large natural variability in the pre-monsoon rains during April and May. The WDs (Western Disturbance) tend to go deeper and impact a large part of the plains, which we just witnessed. This year, we have been getting a lot of disturbances, and most of them have been intense," Dr M Rajeevan, former Ministry of Earth Sciences (MoES) secretary," was quoted by News 18 as saying.

He, however, noted that these are year-to-year variations. "We should be concerned if we see a long-term trend," he said.

Meanwhile, Dr Vivek Gupta, Assistant Professor, at IIT Mandi, told ABP Live that the western disturbances, that originate in the Mediterranean region, bring precipitation to North India between October and April each year.

"Depending on their intensity, duration and location, western disturbances can result in rain, snowfall, cold waves, and even flash floods in the region," he was quoted as saying. He added that the temperature in April can vary from year to year, depending on the development of atmospheric systems.

Are heatwaves in February and rains in April/May the new normal?

The IMD had issued an unprecedented heatwave alert in February for the Konkan and Kutch regions, making it the season’s first alert. This was alarming as a heatwave alert in India usually begins in March.

The then unusual rise in temperature was because of "weak western disturbances and subsequent less rainfall". Skymet Weather Services president GP Sharma had told CNBC-TV18.com that the temperatures are mainly controlled..."over northern or the central part...by the western disturbance, which we know that they start early in the month of November, carry on for December, January and February. Then march onwards, they start shifting towards the north."

Now, weather disturbances, which normally impact the northern region during the January-March period, are now quite active even during April and May when their activity usually abates, News 18 reported.

Though these climate changes sound an alarm, it is not yet proven if these are long-term trend.

More rains are likely in North India

Northwestern states like Punjab, Haryana, Uttar Pradesh and Delhi could also witness scattered rainfall with thunderstorms/lightning/gusty winds over May 6-7. Hailstorm is also likely to occur over Punjab, Himachal Pradesh on May 6 and over Uttarakhand on May 7.

"No heat wave conditions likely over any part of India during next five days," the IMD said on Friday.