This year, sweltering and high temperatures in Jammu & Kashmir and Punjab, unusual heatwaves in Himachal Pradesh, and dry and hot weather across Gujarat and Maharashtra marked the beginning of March — a month that climatologically sees a slow transition from winter to summer. Since last week, however, the heat has been replaced by thunderstorms, hailstorms and rain that have cooled down temperatures. Why did such erratic weather unfold in March? We explain.To understand that, we must first understand Western Disturbances. These are rain-bearing wind systems, originating beyond Afghanistan and Iran, that pick up moisture from the Mediterranean Sea, the Black Sea, the Caspian Sea and the Arabian Sea as they move eastward towards India.WeekAll-IndiaEast & Northeast IndiaNorthwest IndiaCentral IndiaSouth peninsular IndiaFeb 26-Mar 4-86-74-99-999March 5-11-92-85-93-98-92March 12-1866267-19-303.4Since November last year, the Western Disturbance streams affecting India have been subdued in both frequency and intensity, directly affecting rainfall and snowfall.But this trend was broken last week when two successive, intense Western Disturbances (March 13 and 18) crossed northwest, north and eastern India.The severe weather — thunderstorm, lightning, hailstorms, short but intense rain spells (over 115 mm in 24-hours) and snowfall — occurred across the western Himalayas, east and northeast India and some parts of southern India. Neighbouring Pakistan, too, experienced severe weather a couple of days ago.Officials at the India Meteorological Department (IMD) attributed this to not only Western Disturbances but also the prolonged presence of a cyclonic circulation in the lower tropospheric levels. Story continues below this adBesides, there were also strong south-westerly or southerly winds that pumped in moisture from the Bay of Bengal over the region. This led to a confluence of wind over the central and northwest India regions.Weather experts at IMD said similar weather was reported in March 2023.Why do hail and thunderstorms occur commonly in March?A combination of weather factors around mid March resulted in hailstorms across the country. Let’s take a look at these factors.First, Western Disturbances trigger rain (and snowfall in higher altitudes) in the northwest, north, northeast and some parts of eastern India during the non-monsoon months (June-September). This also holds true for early March, when the effect of winter is still lingering.Story continues below this adMarch is also the most favourable month for hailstorms and thunderstorms. Temperatures begin to rise after mid-March and, under the right weather conditions, can trigger thunder, lightning and intense rainfall. A hailstorm in Rewari, Haryana on March 19. PTIIn eastern India, local winds known as Nor’westers (Kalbaisakhi in West Bengal) can lead to the sudden development of intense storms, heavy rain and thunder during this time.Also, when moist winds from either the Bay of Bengal or the Arabian Sea converge with cold winds over central or northwest India, this causes severe weather, particularly over eastern and central India.All these weather factors resulted in hailstorms being reported across a large geographical area — Odisha, Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura Himachal Pradesh, Gangetic West Bengal, Sub-Himalayan West Bengal, Sikkim, Odisha, Jharkhand, Uttarakhand, Punjab, Haryana, western Uttar Pradesh, Chhattisgarh, Madhya Maharashtra, Marathwada in Maharashtra and parts of Karnataka.Story continues below this adHailstorms were reported over Odisha for three consecutive days since Tuesday. Unusually, many areas in Raichur and Dharward districts in north Karnataka were covered under a blanket of hail on March 18.What will the rest of March be like?After an unusually warm start to March with heatwaves sweeping Himachal Pradesh, Gujarat, Kutch, Saurashtra, Maharashtra, Telangana, and parts of Karnataka and Tamil Nadu, the Met department has, for now, said that the thunderstorm activity will ease temperatures.East and northeast India will continue to receive light to moderate rainfall in the remaining days of this month.Also Read | Timely March rain rescues Punjab wheat crop, raises bumper harvest hopeRough and windy conditions with wind speeds ranging 60-80 km/hr will sweep across Jharkhand, Gangetic West Bengal, Jharkhand, Chhattisgarh, Odisha, Bihar till March 21. Story continues below this adTwo more approaching Western Disturbances will start affecting India from March 22 and March 26. The first stream will bring thunderstorms accompanied by gusty winds and moderate rainfall, particularly over sub-Himalayan West Bengal and Sikkim till March 24. Rain in Prayagraj on March 20. PTIThe second stream (March 26) is forecast to be intense. It can cause very heavy rainfall over Sikkim and Gangetic West Bengal till early next week.Largely, the remaining days of March will see thunderstorms and rainfall across the country, keeping the maximum temperatures significantly below normal for this time of the year. Story continues below this adThe severe weather will, in particular, affect the western Himalayan region and northeast India. Meanwhile, the plains of northwest, central and eastern India will see light to moderate rainfall till the end of this month. Above normal rainfall is likely over Telangana, coastal Andhra Pradesh, Kerala and Mahe.