Mumbai sees wettest start to monsoon since 2000 as IMD issues red alert

By July 6, Mumbai had seen more rain than in any year since 2000, and the IMD's red alert warns of more. India Today's Data Intelligence Unit maps the rain and the risk beneath it.

Mumbai is bracing for more. The India Meteorological Department upgraded its warning for Mumbai, Thane, and Raigad to a red alert on Monday, forecasting heavy to very heavy rain and winds gusting to 80 kmph. The red alert runs until July 8; neighbouring Palghar is under an orange alert.

The warning caps a record-breaking start to the monsoon. By July 6, the city's grid had already logged about 1,240 mm of rain this season, the most for this date in 27 years, according to IMD gridded rainfall data analysed by India Today's Data Intelligence Unit. That is about 1.7 times what a normal early July delivers, and it edges past the previous high, set in 2006.

The rain is already biting. Seventeen flights were cancelled, and 365 were delayed at Mumbai airport on Monday, according to airport officials.

A RECORD YOU CAN WATCH BUILD, DAY BY DAY

Rank 2026 against the past 26 monsoons over the same June 1–July 6 window, and it sits first on almost every measure. Its total, about 1,240 mm, is the highest on record for the date. Its wettest five-day spell, more than 750 mm between July 2 and 6, is more than double the typical 350.

The rain is also falling harder per wet day, about 73 mm against a usual 35. By early July, the city had already logged two days that crossed the IMD's "extremely heavy" mark of 204.5 mm — a category that a typical year does not record this early. On July 5 alone, the grid logged more than 225 mm.

THE NUMBER ON THE MAP IS THE CONSERVATIVE ONE

These figures come from IMD's gridded rainfall, which averages rain across cells of about 25 kilometres. The grid tracks the Santacruz gauge closely on seasonal totals, but it smooths out the localised cloudbursts that flood streets. On July 26, 2005, the Santacruz gauge recorded 944 mm in 24 hours; the grid, averaging above its cell, shows 492. So, when the grid reports a record, the rain on the gauges is almost certainly heavier, not lighter.

LESS RAIN, MORE CHAOS

What has changed since 2005 is the ground the rain lands on. Greater Mumbai's built-up area has more than doubled since 1975, rising 119 per cent from 78 to 171 square kilometres, according to the European Union's Global Human Settlement Layer. Concrete does not absorb water; it speeds it into drains built for a smaller, greener city.

That is why the same rain now produces more flooding, and why a downpour smaller than 2005's can still bring the city to a halt.

The monsoon is barely a third over. Mumbai has already had its wettest start in a generation, and the wettest weeks of July and August are still ahead. The record the city should worry about is not the one already on the board. It is the one still being written.

Data notes: Rainfall figures are from IMD's 0.25° gridded daily product for the Mumbai cell.

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