The India Meteorological Department (IMD) has forecast rain and thunderstorms in several districts of south Bengal and Calcutta over the weekend with concerns mounting over the adverse weather’s possible impact on crops.

According to the forecast, incessant rain accompanied by gusty winds will persist from Friday to Monday.

Thursday witnessed overcast skies and intermittent drizzles. The districts of South 24-Parganas, North 24-Parganas, East Midnapore, Calcutta, Howrah, Hooghly, Nadia, Purulia, Bankura, East Burdwan and Birbhum received showers on Thursday.

In an official statement, the Calcutta weather office attributed the adverse weather to a trough extending from north Bangladesh to Telangana across Gangetic West Bengal, interior Odisha and southern Chhattisgarh, reaching up to 1.5km above mean sea level.

“Under its influence, strong moisture incursion from the Bay of Bengal at lower tropospheric levels will trigger thunderstorms, light to moderate rainfall, hailstorms and gusty winds in several districts of south Bengal from February 20 to 23,” the weather office said.

The Met office issued warnings of thunderstorms, lightning and gusty winds reaching speeds up to 40-50kmph with light to moderate rainfall expected in Calcutta, East Midnapore, West Midnapore, Howrah, Nadia, North 24-Parganas and South 24-Parganas over the next four days.

The districts of West Burdwan, West Midnapore, Bankura, Hooghly and Howrah are likely to witness thunderstorms and gusty winds on Friday. Similar conditions will extend to East Midnapore and South 24-Parganas on Friday.

East Burdwan, West Burdwan, Bankura, Birbhum, West Midnapore, North 24-Parganas, Hooghly and Nadia are expected to experience thunderstorms with the wind blowing at 30-40kmph on Saturday.

On Sunday, East Midnapore, West Midnapore, Bankura, Hooghly, Howrah, East Burdwan, Calcutta, North 24-Parganas and South 24 Parganas will witness similar weather.

In north Bengal, Darjeeling is expected to witness snowfall, while widespread rain is predicted in all districts, including Kalimpong, over the weekend.

The sudden spell of unseasonal rain has brought down temperatures, giving rise to a fresh wave of chill. However, concerns have mounted over potential damage to rabi crops.

Agricultural scientists cautioned that potato cultivation might be at the highest risk in case of severe waterlogging.

On Wednesday, embankments along the Roymangal river in Hingalganj, North 24-Parganas, collapsed following incessant rain.

Officials of the agricultural department refrained from immediate assessments. “The weather has just begun to deteriorate with minimal rain so far. It would be premature to comment on the extent of damage,” an official said.

District administration officials said most rain-sensitive crops, such as mustard and wheat, had already been harvested while farmers were advised to harvest the remaining produce as soon as possible.

Joydip Mukherjee, deputy director of agriculture, (Nadia), said: “Around 70 per cent of mustard, the main rabi crop in Nadia, has already been harvested. We have alerted farmers and hope they will complete the harvest before the predicted spell of rain on February 22.”

Many agricultural experts and farmers believe that unless heavy rainfall leads to severe waterlogging, showers might benefit crop growth. “There has been a prolonged dry spell over the past few months. This rain will help moisten the soil,” an official said.

For horticultural produce, the officials said the extent of potential losses could only be assessed 24 hours after the predicted rainfall.

“Weather conditions also change suddenly. So it would not be prudent to speak so early now. We have issued necessary instructions to overcome or minimise possible damage as far as possible,” an official of the horticulture department said.