Commuters wade through a flooded street after heavy rain showers in Mumbai on May 26. (Photo credit: Punit Paranjpe/AFP/Getty Images via CNN Newsource)

(CNN) — India’s financial capital and one of its largest cities has experienced its wettest May in more than a century, with the unusually early arrival of the monsoon season causing a ferocious weekend downpour that turned roads into rivers and flooded a newly inaugurated underground train station.

Mumbai, a city of more than 12 million, has recorded more than 400 millimeters of rainfall this month so far, according to data from the Indian Meteorological Department (IMD), with much of the downpour arriving late last weekend.

The deluge caused chaos and delays across transport networks, including at the newly inaugurated Worli Metro Station.

Commuters lie stuck in traffic as they wade through a flooded street after heavy rain showers in Mumbai on May 26. (Photo credit: Punit Paranjpe/AFP/Getty Images via CNN Newsource)

Video published by local media outlets showed travelers wading knee-deep in flood water, water gushing down a station staircase, and water leaking heavily from the ceiling onto a train platform.

India’s $4 trillion economy is heavily dependent on the monsoon, which brings rains that farmers depend on to support the country’s agricultural sector, which employs nearly half of the country’s 1.4 billion people.

The rains, which usually arrive in June and last through September, are needed to grow crops, irrigate farmland and replenish India’s reservoirs. But this year’s early arrival has caused havoc across Mumbai, India’s finance capital and home to its vaunted Bollywood film industry, flooding roads and submerging cars.

Some experts say that global warming is increasing the variability of India’s monsoon rains faster than previously projected.

People wade through waterlogged road at Gandhi Market in the Sion area after heavy rain on May 25, in Mumbai, India. (Photo credit: Raju Shinde/Hindustan Times/Getty Images via CNN Newsource)

Sushma Nair, a scientist at the India Meteorological Department (IMD), told CNN the city’s Colaba observatory had recorded its wettest May since 1918.

The onset of the southwest monsoon in Mumbai on May 26 is the earliest advancement over the city since 1950, Nair said.

Each year the monsoon causes chaos across Mumbai, particularly for commuters travelling on its hectic, overcrowded public transport system.

Last year in May, heavy rains caused a huge billboard to collapse, killing at least 14 people and injuring dozens more.

Prime Minister Narendra Modi inaugurated the Worli Metro station just earlier this month, part of his ambitious plan to modernize India’s aging transport network and transform the country’s infrastructure to achieve his goal of turning it into a developed nation by 2047.

Vehicles wade through waterlogged road at Gandhi Market in the Sion area after heavy rain on May 25, in Mumbai, India. (Photo credit: Raju Shinde/Hindustan Times/Getty Images via CNN Newsource)

Further rains are forecast for the region this week, the IMD said, potentially causing further flooding.

The southern state of Kerala over the weekend also saw an unusually early arrival of the monsoon, bringing some respite after experiencing days of an unrelenting heatwave.

Indian capital New Delhi last week also experienced widespread rain, lightning, and thunderstorms, causing a canopy at the city’s airport to collapse from waterlogging.

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