The Regional Meteorological Centre in Alipore has forecast Nor'wester activity, locally known as 'Kalbaisakhi', beginning Thursday and continuing into Friday.

According to the weather office, scattered thunderstorms accompanied by rain are likely across most districts of West Bengal, including Kolkata.

A yellow alert has already been issued for Howrah and South 24 Parganas, with predictions of moderate rainfall and gusty winds reaching speeds of 30 to 40 kmph.

An orange alert has been sounded in six south Bengal districts, North 24 Parganas, Bankura, East Burdwan, West Burdwan, Nadia, and Birbhum, indicating a higher intensity of weather activity.

These areas may experience thunderstorms with lightning and stronger winds, potentially reaching up to 50 kmph.

Weather system triggers statewide impact

Meteorologists attribute the sudden shift in weather to an active trough stretching from eastern Uttar Pradesh to Manipur, passing through Bihar and parts of Gangetic West Bengal.

Additionally, a cyclonic circulation over northeastern Bangladesh at an altitude of around 0.9 km above sea level is influencing atmospheric conditions.

Due to this combination of systems, thunderstorms are expected to persist across multiple districts even beyond Friday.

Higher chances of intense activity have been predicted in Purulia, Bankura, West Midnapore, Jhargram, East and West Burdwan, Birbhum, and Murshidabad.

North Bengal districts, including Darjeeling, Kalimpong, Alipurduar, Cooch Behar and Jalpaiguri, are also likely to witness light to moderate rainfall with thunderstorms and gusty winds of 30 to 40 kmph.

Similar scattered thunderstorm activity is expected in Malda and the Dinajpur districts.

Heat to dip briefly before rising again

While the incoming storms are expected to bring temporary relief, the respite may be short-lived.

The weather department has indicated that temperatures will dip slightly on Friday due to cloud cover and rainfall, but are likely to rise again over the weekend.

Kolkata's maximum temperature may hover around 36 degrees Celsius, while western districts could see mercury levels touching 40 degrees Celsius during the day.

The overall trend suggests a gradual increase of 2 to 3 degrees Celsius in South Bengal over the next three days.

From April 19 to 25, hot and humid conditions are expected to dominate parts of south Bengal due to dry westerly and northwesterly winds combined with rising seasonal heat.

Districts such as Purulia, Bankura, West Burdwan, Jhargram, and West Midnapore are likely to experience particularly uncomfortable weather.

Rain pattern uneven across regions

The rainfall distribution across Bengal is expected to remain uneven. On April 20, isolated light rain or thundershowers may occur in Jhargram, West Midnapore, Birbhum, and Murshidabad, while other districts are likely to remain dry with persistent humidity.

Dry weather is forecast to prevail across most parts of South Bengal on April 21 and 22, with intensifying heat conditions.

However, by April 23, light rain or thundershowers may return to several districts, including Birbhum, Murshidabad, Nadia, North 24 Parganas, and parts of Burdwan, Purulia, Bankura and Jhargram.

In contrast, North Bengal is expected to experience more consistent rainfall activity over the coming days, providing relative relief from heat compared to the southern districts.

Overall, while the arrival of Kalbaisakhi storms brings a welcome break from the oppressive heat, the relief is expected to be temporary.

With temperatures set to climb again and humidity levels remaining high, residents across south Bengal are likely to continue facing challenging weather conditions in the days ahead.