The first spell of post-monsoon rain is expected to sweep across West Bengal from Friday as a low-pressure area, now active over the southwest Bay of Bengal adjoining the Tamil Nadu–Andhra Pradesh coast, begins to draw moisture towards the eastern parts of the country.
The system, which formed earlier this week, is likely to move northwestward while steadily expanding its influence over the Bay region. Moisture-laden winds from the sea are expected to travel north and northeast, reaching Odisha and Gangetic West Bengal by Thursday night or early Friday. Under its influence, several districts in southern Bengal, including Kolkata, Howrah, Hooghly, East and West Midnapore, and South 24 Parganas, are likely to receive scattered rain and thundershowers during the weekend.
Although the southwest monsoon has already withdrawn from West Bengal, this fresh spell will mark the beginning of the post-monsoon rain phase for the state. The initial rainfall is likely to be light to moderate in most places, but isolated pockets may witness brief heavy showers accompanied by thunder and gusty winds.
Meteorological models further indicate that another low-pressure system is likely to form over the central Bay of Bengal around October 28 or 29. Early projections suggest that this second system could be stronger, pulling in deeper moisture from the sea and leading to a more widespread and intense spell of rain across coastal Bengal and adjoining Odisha. Should the system move closer to the east coast, heavier rain and extended cloudy conditions may continue into the first week of November.
In Kolkata, weather conditions are expected to change gradually from midweek. The city is likely to experience partly cloudy skies and a rise in humidity from Thursday, followed by scattered showers from Friday afternoon. The rain may increase in frequency and intensity over the weekend. Daytime temperatures are expected to hover between 31 and 33 degrees Celsius, while nights are likely to remain warm and sticky around 25 degrees.
With the withdrawal of the monsoon complete, this transitional phase marks Bengal’s entry into the post-monsoon season—a period known for brief yet intense spells of rain triggered by Bay systems. Such rain events are typical of late October and early November, when the Bay of Bengal remains warm and conducive to low-pressure formation.
The upcoming spell is therefore being seen as the start of the seasonal shift, with the possibility of a prolonged wet phase if the second system materialises as predicted.