Moderate to severe thunderstorm activity likely to commence from Saturday afternoon in Bengal, according to the India Meteorological Department’s latest forecast that will come as a relief to large parts of the state reeling from the heatwave.

The region will initially continue to experience mainly dry westerly to northwesterly winds, leading to heatwave and hot and humid conditions across the state through Saturday, the IMD said in its special bulletin.

However, the wind pattern is expected to change by afternoon due to favourable wind patterns and moisture incursion from the Bay of Bengal, triggering thunderstorms in several districts.

Temperature and humidity forecast

The maximum temperature across South Bengal and Malda district is anticipated to stay 3 to 5°C above normal through Saturday.

Coastal districts are expected to record maximum relative humidity levels between 80-90 per cent, while interior districts will likely observe relative humidity between 70-80 per cent.

Minimum relative humidity is projected to be around 45-55 per cent in coastal areas and 30-45 per cent in the interior regions.

Over the past 24 hours, heatwave conditions prevailed at one or two places in West Burdwan district of South Bengal and Malda district of North Bengal, according to the IMD.

Maximum temperatures were 3-5°C above normal at most places in North Bengal and at a few places across South Bengal.

Kalaikunda in West Midnapore and Purulia in South Bengal recorded the highest maximum temperature of 44.5°C, while Malda in North Bengal registered 40.5°C.

Heatwave warning for south Bengal

On April 26, heatwave conditions, characterized by maximum temperatures of 40°C or more and above normal by 5°C or more, are likely to occur at one or two places in West Burdwan, Purulia, Bankura and Jhargram districts.

Hot and humid weather conditions are also likely at one or two places in Murshidabad, East Bardhaman, Nadia and Hooghly districts.

Heatwave warning for north Bengal

Similarly, a heatwave is likely to occur at one or two places in the Malda district of North Bengal on April 26, with maximum temperatures reaching or exceeding 40°C and exceeding the normal by 5°C or more.

Thunderstorm and gusty wind warnings for south Bengal

Starting Saturday afternoon, thunderstorms accompanied by gusty winds reaching speeds of 40-50 kmph, lightning and light to moderate rainfall are likely at one or two places in Purulia, Jhargram, Birbhum, Murshidabad, Bankura, West Midnapore and both East and West Bardhaman districts.

On April 27, thunderstorms with gusty winds of 50-60 kmph, lightning and light to moderate rain are expected in Birbhum, East Bardhaman, Murshidabad, Nadia and North and South 24 Parganas districts.

Hailstorms are likely at one or two places in East Bardhaman and Nadia districts.

For the remaining districts, thunderstorms with gusty winds (40-50 kmph), lightning and light to moderate rain are likely.

On April 28, thunderstorms with gusty winds of 60-70 kmph, lightning and light to moderate rainfall are expected over Purulia, Bankura, West Burdwan, Hooghly, Jhargram and West Midnapore districts, with heavy rainfall (≥7 cm) likely at one or two places over West Midnapore.

Other districts will also experience similar thunderstorm activities, with East Bardhaman also expected to receive heavy rainfall.

On April 29, thunderstorms with gusty winds of 40-50 kmph, lightning and light to moderate rainfall are likely across the districts.

On April 30, thunderstorms with gusty winds of 30-40 kmph, lightning and light to moderate rainfall are expected across all districts.

Thunderstorms with gusty winds of 40-50 kmph, lightning and light to moderate rainfall are expected across all districts of North Bengal on Saturday.

On Sunday, gusty winds increasing to 50-60 kmph, lightning and light to moderate rainfall are likely across North Bengal districts.

Heavy rainfall (7-11 cm) is anticipated at one or two places in Jalpaiguri, Alipurduar and Darjeeling districts.

On Monday, thunderstorms with gusty winds of 40-50 kmph, lightning and light to moderate rainfall will continue across the districts, with heavy rainfall likely at one or two places in North Dinajpur and Darjeeling districts.

On Tuesday, gusty winds (30-40 kmph) with lightning and light to moderate rainfall are forecasted for Malda, North Dinajpur, Darjeeling and Jalpaiguri districts.

Possible impacts and suggested actions

The heatwave conditions pose a moderate health concern for vulnerable populations, including infants, the elderly, people with chronic illnesses and those exposed to the sun for prolonged periods or engaged in heavy work.

The general public may experience heat cramps and heat rashes.

Authorities have advised people to avoid prolonged heat exposure and outdoor activities between 11 AM and 4 PM.

Individuals are encouraged to wear lightweight, light-coloured, loose cotton clothes and to cover their heads with a cloth, hat or umbrella.

Staying hydrated by drinking sufficient water even when not thirsty is strongly recommended.

Symptoms like weakness, dizziness, headache, nausea, sweating or seizures should be taken seriously and medical help must be sought immediately.

Thunderstorms and associated gusty winds may cause damage to standing crops, vegetables and horticulture produce.

There is a possibility of lightning strikes, especially in open fields and damage to loose or unsecured structures.

Traffic disruptions are also likely in urban areas.

Citizens are advised to take shelter in safe places during thunderstorm activity, avoid taking shelter under trees or electric poles and avoid contact with water bodies.

Movement of traffic should be regulated carefully during thunderstorms to ensure public safety.