IMD maps dated 8 October 2026: Kolkata and south Bengal forecast windows in IST. Rainfall coverage is not the probability at one location; later updates may change the forecast.
IMD maps dated 8 October 2026: Kolkata and south Bengal forecast windows in IST. Rainfall coverage is not the probability at one location; later updates may change the forecast.

Mahalaya falls on Saturday, 10 October 2026, according to IMD’s Kolkata festival calendar. For Kolkata and south Bengal, the weather maps dated 8 October show scattered rainfall for the period ending at 8:30am IST on October 10, followed by isolated rainfall for the next 24 hours. A plan for dawn therefore falls under a different forecast window from a plan later that morning.

This distinction matters as families arrange travel and observances before the festival season. Reports on October 7 described wet weather leading up to Mahalaya, but an earlier warning is not automatically a warning for the whole of October 10. The current maps have both an issue date and a validity period; this report uses those printed periods rather than an AI summary’s single daily forecast.

Read the two windows before choosing an outdoor time

From 8:30am on October 9 to 8:30am on October 10, the south Bengal rainfall map is marked SCT, or scattered rain. Kolkata is also in a yellow “watch” area on the warning map for that period, with isolated thunderstorm and lightning symbols. Before-dawn activity on Mahalaya remains inside that window, rather than the map labelled Day 3.

From 8:30am on October 10 to 8:30am on October 11, the rainfall map marks West Bengal as ISOL, or isolated rain. The warning map covering Day 3 to Day 7 is marked “No Warning”. These two signals can coexist: an absence of a warning is not a forecast of no rain at every location. South Bengal is shown dry in the following window, from 8:30am on October 11 to 8:30am on October 12.

A coloured percentage describes coverage, not your personal odds

IMD groups spatial distribution as isolated at 25% or less, scattered at 26–50%, fairly widespread at 51–75%, and widespread at 76–100%. Its terminology defines these as the share of stations reporting or expected to receive rain in a region. Reading ISOL as a 25% probability of rain at your home or a particular riverbank changes the meaning of the forecast.

The maps also do not identify a guaranteed dry hour, the exact rain total at a venue, or the cause of every local shower. We therefore do not attach an unverified temperature, rain probability or storm track to the Mahalaya date. A useful decision combines the correct time window with a local update close to departure.

Use the official update to make a practical plan

For an early outing, keep rain protection and an indoor alternative ready, and check IMD Kolkata’s latest forecast and warnings before leaving. If a local warning or storm interrupts an exposed outdoor activity, postpone it or move the plan indoors. These are planning measures prompted by the warning, not a claim that all observances or transport services will be disrupted.

The official forecast PDF below is updated in place, so its printed issue date must be read again on October 9 or 10. The calendar also lists the start of Sharadiya Navaratri on October 11; that is a separate date from Mahalaya. The key follow-up is whether a newer map changes Kolkata’s warning or rainfall window. Until then, preserve the distinction between rain coverage, a warning and a guarantee about a particular location.

Sources & context

Based on IMD maps dated 8 October 2026 and its festival calendar; spatial rainfall categories refer to station coverage, not the chance of rain at one address.

AI assisted with drafting and editing. This article is part of our preview edition. Editorial standards & corrections →