Mumbai Rains: Early warning systems and adaptation plans are the only option

PHOTO COURTESY: arise.tv

As Mumbai reels under one of its heaviest August rain spells in recent years—crossing 800 mm of rainfall by August 19, 2025 against a monthly average of 560.8 mm—experts are warning that such events will only grow more frequent and intense in a warming world. Streets turning into rivers and vehicles submerged have become familiar images every monsoon, but the science behind it is now clearer than ever.

After the remaining rain deficit for July, spell of extremely heavy rains returned to the city around August16 Mumbai recorded over 800 mm of rainfall till the afternoon of August 19, 2025, surpassing its monthly average rainfall of 560.8 mm.

A new briefing, “Mumbai Rains: Early warning systems and adaptation plans are the only way out”, by Climate Trends brings together leading voices who highlight how:

• Climate change is acting like a steroid—rising average temperatures and warming the Arabian Sea, intensifying moisture influx into the city

• Despite improved forecasts, gaps in coordination and communication mean citizens often don’t get timely alerts

• Early warning and nowcasting systems need to be citizen-centric, supported by robust drainage upgrades, green cover, and flood mapping

• Need for urban flood action plans, using rainfall data and risk mapping to design resilient responses.

The experts agree: advance warnings, better planning, and adaptation are Mumbai’s only way forward to protect lives, livelihoods, and critical infrastructure.

After remaining rain deficit in July, the spell of extremely heavy rains returned to the city around August16. Mumbai recorded over 800 mm of rainfall till the afternoon of August 19, 2025, surpassing its monthly average rainfall of 560.8 mm.

Multiple weather systems activated the Monsoon surge that resulted in torrential rains over parts of coastal Maharashtra, including Mumbai. The axis of the monsoon trough is presently passing through Diu, Surat, Nandurbar, Amravati, and the centre of the depression over South Odisha towards the Central East Bay of Bengal.

According to Vice President of Meteorology And Climate Change at Skymet Weather Services, Mahesh Palawat says “A low-pressure area over the Vidarbha region, a cyclonic circulation over the Northeast Arabian Sea and Southeast Gujarat, a depression over the Bay of Bengal and adjoining Odisha and an active off- shore Monsoon trough running along the West Coast from Konkan region to North Kerala have resulted in vigorous Monsoon conditions over Coastal Maharashtra, particularly Mumbai. Whenever multiple weather systems align together, they tend to complement each other, intensifying weather activity.”

Meanwhile, Climate Scientist, Dr Raghu Murtugudde, Emeritus Professor, University of Maryland & Retired Professor, IIT-Mumbai said while three-digit rainfall is not new to the city, climate change has a role to play. “While there is a natural variability of monsoon weather systems, climate change acts like a steroid. The northward swing of the southwesterly monsoon winds are pumping massive amounts of moisture from the warm Arabian Sea into northern Western Ghats. This northward swing is a combination of global warming, especially the warming over the Middle East, and the natural variability of the monsoon winds.”

According to a recent study, moisture supply for the summer monsoon rainfall along the west coast of the Indian subcontinent is mainly transported from the Arabian Sea. The Middle East warming is almost two times faster than other inhabited parts of the world and has been causing a dramatic increase in atmospheric instability in the Arabian Sea by thrusting moisture supplies northward. Consequently, the regions of Northwest India have been vulnerable to unprecedented rainfall. The land heating across the Middle East has been responsible for 46% of the intensified rainfall over Northwest India and Pakistan during 1979–2022.

“Mumbai’s torrential downpour is the result of strong monsoon winds lashing the city, intensified by the combined pull of a low-pressure system over east India and another over the Gulf of Khambat. This sudden burst of rain follows the city’s driest July since 2015, which failed to meet its monthly average rainfall. Whilst the exact role of climate change in this particular event will need to be assessed through scientific studies, the overall trend is evident: more intense rainfall occurring over shorter durations is consistent with what we expect in a warming world. Extreme weather events like this are becoming increasingly common, and Mumbai needs to find a way forward to adapt and build resilience against such extreme events,” said Dr Akshay Deoras, Research Scientist, National Centre for Atmospheric Science, University of Reading, UK.

Advance warnings, the only way out: Experts warn : there has been a rise in temperature due to global warming. Secondly, the exponential warming of the Arabian Sea has increased the moisture influx along the West Coast, contributing to heavy precipitation. In this scenario, the only way out is to have a very good network of early warning systems, nowcast systems for urban flooding.

“These advance warning systems should be citizen-centric, which means the information should reach out to people so informed decisions can be taken. IIT Mumbai has created the Mumbai Flood Monitoring System which helps in disseminating timely information to various stakeholders,” said Dr Subimal Ghosh, Institute Chair Professor, Department of Civil Engineering & Convener, Interdisciplinary Program in Climate Studies-IIT Mumbai.

“While forecasting has been improving, coordination between the multiple working agencies is still a challenge. If the information is not disseminated at the right hour, then we will also fail the purpose timely forecasting. With extreme weather events now being regular visitors, we need to identify high-risk zones or flood-prone areas in the city. There should be an evacuation process as well as a well-defined escape route. This cannot be done overnight,” said K. G. Ramesh, Former Director General- India Meteorology Department.

An IDF (Intensity-Duration-Frequency) curve is a graphical representation of the statistical relationship between rainfall intensity, duration, and frequency of occurrence. Council on Energy, Environment and Water (CEEW) had prepared a Thane City Action Plan for Flood Risk Management 2024, offering a framework for administrators to strengthen preparedness, response, and mitigation measures against urban floods. Based on a detailed analysis of 52 years of rainfall data, the plan develops intensity-duration-frequency curves, estimates peak flow discharges, and creates a ward-wise urban flood risk index to identify vulnerable hotspots. It further provides actionable short-, medium-, and long-term recommendations for both monsoon and non-monsoon phases, aimed at enhancing the city’s adaptive capacity and guiding its transformation into a flood-resilient smart city.

“If you account for total natural disasters that have happened and the extent of loss and damage, then floods rank on top. India’s megacities have not been spared the consequences of the changing monsoon pattern. Vehicles in Mumbai are submerged, and people wade through knee-deep water that is lashing the city is a recurrent phenomenon that did not take its 12 million residents by surprise –streets turning into rivulets has become a familiar pattern every monsoon. IPE Global is supporting BMC in developing a robust real-time AI-ML enabled Multi-Hazard Risk Atlas for Mumbai, which will help build resilience and ensure preparedness by climate-proofing the lives, livelihoods and infrastructures in the financial capital of India.” says Abinash Mohanty, Global Sector-Head Climate Change and Sustainability, IPE Global and an Expert Reviewer of the IPCC AR(6).

The writer of this article is Dr. Seema Javed, an environmentalist & a communications professional in the field of climate and energy