Pune/Mumbai: Maharashtra is poised to witness its earliest monsoon onset in 12 years, with the India Meteorological Department (IMD) forecasting favorable conditions for the Southwest Monsoon to advance into parts of the state within the next 2-3 days – potentially matching the early arrival pattern last seen in 2011 and 2013.Meanwhile, the weather office on Saturday issued a yellow alert indicating thunderstorms and rainfall for Mumbai and Thane districts from May 24 through May 27.The development comes after the Southwest Monsoon set in over Kerala on Saturday, eight days ahead of its normal date of June 1. IMD officials said conditions are now favorable for further advance of the monsoon into some more parts of central Arabian Sea, entire Goa, some parts of Maharashtra and Andhra Pradesh, some more parts of Karnataka, remaining parts of Tamil Nadu, and northeastern states during the next 2-3 days.“This is the earliest monsoon advance in years for Maharashtra, similar to Kerala, where the monsoon set in on Saturday—eight days ahead of the normal onset date,” said S.D. Sanap, IMD scientist, Pune.The monsoon normally enters Maharashtra after June 5. However, IMD officials emphasized that the monsoon onset declaration depends on maintaining a “line of continuity” across regions.“We should also see good rainfall in adjoining areas such as parts of northeast India, Karnataka, and Andhra Pradesh. That is also a factor,” explained another IMD official.This continuity principle means that for monsoon to be declared over Maharashtra, sustained rainfall patterns must be established across interconnected geographical zones, not just isolated pockets. The monsoon system needs to show consistent progress across the Western Ghats and adjoining areas to ensure it’s a genuine advance rather than pre-monsoon activity.Sanap added, “Monsoon normally advances over Goa around June 5, but our forecast indicates that the entire Goa could be covered in the next 2-3 days, so naturally onset would occur much earlier in Maharashtra too.” As per normal advancement dates, the monsoon covers the entire state by June 15.According to historical data, Maharashtra’s monsoon onset dates have typically fallen in June over the past decade and a half. The earliest onset in recent years was June 4 in both 2011 and 2013. If the monsoon advances as predicted in the next 2-3 days, 2025 could potentially see the state’s earliest onset since 2011. IMD scientists refrained from specifying which cities in Maharashtra could see monsoon advancement first, stating that onset declaration considers multiple factors including wind patterns, rainfall distribution, and regional continuity of the weather system.