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Monsoon arrives in Mumbai; earliest in 75 years, says IMD official

The southwest monsoon usually makes its onset over Kerala by 1 June and reaches Mumbai by 11 June

People wade through water amid rains at Byculla, Mumbai (photo: PTI )
People wade through water amid rains at Byculla, Mumbai (photo: PTI ) 

The southwest monsoon has set in over Mumbai 16 days before the usual date, making it the earliest since 1950, the India Meteorological Department (IMD) said on Monday.

The primary rain-bearing system reached Kerala on Saturday, marking its earliest arrival over the Indian mainland since 2009, when it reached the southern state on 23 May.

The southwest monsoon usually makes its onset over Kerala by 1 June, reaches Mumbai by 11 June and covers the entire country by 8 July. It starts retreating from northwest India around 17 September and withdraws completely by 15 October.

According to the IMD's Mumbai office, the data available since 1950 shows that this is the earliest arrival of the monsoon in the city. Brihanmumbai Municipal Corporation records show that between midnight and 11.00 am on Monday, several parts of south Mumbai (Island City division) received over 200 mm of rainfall.

Last year, the monsoon reached Mumbai on 25 June. In preceding years, it arrived on 11 June in 2022, 9 June in 2021, 14 June in 2020, and 25 June in 2019. In 2020, the onset occurred on 14 June, while in 2021 it arrived on 9 June.

As heavy rains lashed Maharashtra, the IMD issued a ‘red alert' for Mumbai, and neighbouring districts of Thane, Raigad, and Ratnagiri, warning of “extremely heavy rainfall and thunderstorms with lightning and gusty winds at isolated places”.

The weather department had earlier upgraded its alert from ‘yellow’ to ‘orange’ for Mumbai, Thane and Raigad. The red alert will remain in place until Tuesday morning.

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The rains have caused waterlogging and more than usual traffic congestion in several parts of Mumbai. The city woke up to heavy rains and dark clouds, with the coastal observatory in Colaba recording 135 mm of rainfall by 8.30 am, IMD said.

Meteorologists emphasise that the date of monsoon's onset has no direct correlation with the total seasonal rainfall.

The monsoon arriving early or late in Kerala or Mumbai does not mean it will cover other parts of the country. It is characterised by large-scale variabilities and global, regional and local features.

The IMD in April had made a forecast of above-normal cumulative rainfall in the 2025 monsoon season, ruling out the possibility of El Niño conditions which are associated with below-normal rainfall in the Indian subcontinent.

Rainfall between 96 per cent and 104 per cent of the 50-year average of 87 cm is considered 'normal', the IMD states.

Rainfall less than 90 per cent of the long-period average is considered 'deficient'; between 90 per cent and 95 per cent is 'below normal'; between 105 per cent and 110 per cent is 'above normal'; and more than 110 per cent is considered 'excess' precipitation.

India saw 934.8 mm of rainfall in 2024, 108 per cent of the average. In 2023, it recorded 820 mm, 94.4 per cent of the average. In 2022, it saw 925 mm; 870 mm in 2021; and 958 mm in 2020, according to IMD data.

The monsoon plays a critical role in India’s agriculture-dependent economy, providing vital water for crops, replenishing reservoirs, and supporting drinking water and hydropower generation. Agriculture supports the livelihood of around 42 per cent of the population and accounts for 18.2 per cent of the country's GDP.

With PTI inputs

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