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The weather conditions over India in March and April have been characterised by the expected heat waves, thunderstorms and hailstorms along with unexpected rainfall in some regions, especially in the Northeast and southern parts of the country.
The immediate meteorological causes for such weather were the continuous activity of western disturbances throughout the period, along with other weather systems such as cyclonic circulations, low pressure troughs and the sub-tropical westerly jet stream among other temporary wind systems. The moisture for the excess rains was contributed by two anti-cyclonic systems active over the Bay of Bengal and Arabian Sea which were active much ahead of schedule in 2026.
In March 2026, there was heavy rainfall (7-11 cm) over at least one place in the country on around 20 days, according to an analysis of India Meteorological Department (IMD)’s data by Down To Earth (DTE). Many regions consistently suffered from thunderstorms and some regions also experienced hailstorms. There were heat waves and hot and humid conditions over many regions at the beginning of March which ceased after the storm activity began.
“Around the end of February, many regions of India started experiencing above normal day time temperatures,” K J Ramesh, climate scientist and former director general of IMD, told DTE. “The natural response for this kind of heating is the development of thunderstorms which could carry dust, lighting, hail or rainfall depending on localised meteorological conditions. Thunderstorms are the only process for nature to abate the heating,” he added.
Since the end of February and into early March, daytime temperatures in many regions across the country started being 3-5°C above normal. On some of the days, they were as high as 8-12°C above normal. This heating over four to five days is enough to create conditions for thunderstorm formation. “The warming also increases the moisture holding capacity of the atmosphere and in the presence of a source of moisture, the thunderstorms can also carry a lot of rainfall,” said Ramesh.
There was heavy to very heavy rainfall over 18 states and two Union territories in the month of March, according to data from IMD, analysed by DTE. Most of this rainfall occurred over all the Northeastern states which have been experiencing below normal rainfall for the past many seasons. All the Northeastern states had excess rainfall in March, according to IMD data.
The highest excess rainfall was in Nagaland at 131 per cent, followed by Assam at 129 per cent. The lowest excess was in Arunachal Pradesh of 4 per cent of the average. States in eastern India like Odisha, West Bengal and Bihar also received heavy rainfall on at least one of the days. West Bengal received 231 per cent excess rainfall in March and Bihar received 215 per cent.
In the southern Peninsula as well, all the states received heavy rainfall on at least one of the days. Karnataka received 136 per cent excess rains in March. Gujarat in the west and Jammu and Kashmir and Uttarakhand experienced heavy rains as well.
On 27 days of March, at least one western disturbance was active over India. There were a total of eight western disturbances during the month. Along with the western disturbances, there were other weather systems such as cyclonic circulations, low pressure troughs, the subtropical westerly jet stream and other wind systems. There were between five to 13 weather systems active over India and the surrounding seas on each of the days of March. Some of the low pressure troughs were reminiscent of the monsoon period rainfall-inducing systems in geographical spread and strength.
“In the same duration as these weather systems over land, a quasi-permanent anti-cyclone or a high pressure area in the atmosphere was also present over the Bay of Bengal,” said Ramesh. Anti-cyclones are large systems in the atmosphere with winds flowing in a clockwise direction. “Their direction brought the winds onshore along the eastern coast of India and they carried moisture with them. These conditions enabled the formation of thunderstorms along with heavy rainfall in these regions,” he added.
At the same time, there was another quasi-permanent anti-cyclone over the northern Arabian Sea, according to Ramesh. The incoming western disturbances formed deep troughs starting from Iran and Afghanistan in the beginning and later over Pakistan and northwest India. “When the western disturbance related troughs were over Iran and Afghanistan, the anti-cyclone pushed moisture into the Persian Gulf causing thunderstorms with rainfall in that region. As the trough moved over Pakistan, its bottom part was over the northern Arabian Sea and took moisture directly from there. Deeper troughs associated with stronger western disturbances can pull more moisture from the sea,” said Ramesh.
Similar weather systems were active over the country in April as well with the addition of anti-cyclonic circulation over central and southern regions on most of the days and the absence of the activity of the subtropical westerly jet stream on all but two days. On 20 out of the 23 days, at least one western disturbance was influencing the weather of the country, especially in northwest and some central and northeastern regions.
Thunderstorms were the most prevalent extreme weather events, with hailstorms on many of the days. The days with heavy rainfall and their geographical spread were less as compared to March as heating started again in northwest and eastern India.
“Moisture loading in these regions has changed significantly in the current pre-monsoon season. As there is above normal warming of the atmosphere, there is above normal moisture as well,” concluded Ramesh. Moisture loading refers to the process by which atmospheric weather systems collect, ferry and concentrate water vapour. It is mainly driven by evaporation.