Monsoon mayhem: Why has Mumbai seen its wettest start to July in decades?

Mumbai has already received over 60% of its seasonal monsoon rainfall, the highest for early July in 27 years. Here's why the city is seeing such extreme rain.

In Short

• Mumbai received 1,240 mm rain since June 1, highest in 27 years
• Rapid urbanisation worsens flooding and drainage issues
• Monsoon to stay active with more heavy rain and flood risks

Mumbai's monsoon has been nothing short of relentless and extreme this year.

Torrential rain has flooded roads, disrupted suburban trains and flights, uprooted trees, triggered landslides and forced schools, colleges and several government offices to shut.

With the rate and intensity with which it's raining in Mumbai, it's no surprise that the city has already received an extraordinary amount of rainfall.

According to the India Today Data Intelligence Unit (DIU), which analysed IMD's rainfall data, Mumbai had received around 1,240 mm of rain between June 1 and July, making it the highest for this period in 27 years.

By July 6, the city had also received more than 60% of its average seasonal monsoon rainfall, even though nearly three months of the rainy season are still left.

WHY IS IT RAINING SO MUCH IN MUMBAI?

Several weather systems have aligned to produce the exceptional rainfall.

An active southwest monsoon, a well-marked low-pressure system, the monsoon trough remaining close to the west coast, and continuous moisture-laden winds from the Arabian Sea have together fuelled persistent rain-bearing clouds over the region.

According to the India Today DIU analysis, the city received more than 750 mm of rain between July 2 and July 6 alone. During this period, Mumbai experienced two days of "extremely heavy" rainfall, a category the IMD defines as 204.5 mm or more in 24 hours.

On July 5, IMD's rainfall data showed parts of the city receiving over 225 mm of rain.

Weather stations tell a similar story.

By July 6, IMD's Santacruz observatory had recorded 898.4 mm of rainfall, while Colaba had received 823.4 mm, both already exceeding their respective average rainfall for the entire month of July.

FLOODED NEIGHBOURHOODS AND MORE RAIN

As rain pours, the city has seen constant waterlogging and disruptions.

The analysis blamed the rapid urbanisation for it, noting that open land has given way to roads and buildings, less rainwater is absorbed into the ground and more flows rapidly into drains originally designed for a much smaller city.

This rapid urbanisation means that even rainfall well below the record-breaking levels in 2005 can overwhelm drainage systems, inundate low-lying neighbourhoods and disrupt transport within hours.

The IMD says the southwest monsoon is likely to remain active over the Konkan region for the next few days, with further spells of heavy to very heavy rainfall expected.

As a result, Mumbai is likely to remain vulnerable to flooding, transport disruptions, landslides and other rain-related hazards as the peak monsoon season continues.

- Ends