They are akin to aliens in the world of meteorology—unimaginable and unpredictable. And now they seem to be invading. That, at least, was how it felt when cloudburst-like downpours lashed much of India’s plains in the monsoon months of August and September.
Meteorologists define cloudburst as rainfall exceeding 100 mm in an hour over an area of 20 to 30 sq km. Such events are typically confined to hilly terrain. But on August 30, the Manali area of Chennai, Tamil Nadu’s coastal capital, recorded 106 mm of rain in an hour starting at 10 pm. A second spell, from 11 pm to midnight, brought another 127 mm. In the same hour nearby Wimco Nagar saw over 157 mm of rainfall, Korattur recorded 137 mm, and New Manali received 103 mm of rains. The city as a whole experienced five cloudbursts or cloudburst-like events within two hours. Just two days earlier, Kamareddy city of Telangana, had endured 576 mm of rain in 48 hours—its heaviest downpour in 35 years. Much of it fell within just a few hours.
Meteorological records show that several blocks of the district received more than 300 mm during that period. Such rain events also struck other states. Rain-shadowed Nanded, in Maharashtra, received 206 mm rainfall on August 17-18. Between the mornings of September 22 and 23, Kolkata was drenched with 251 mm of rainfall—highest for any September day in the last 39 years and the sixth highest in the city’s history. Of this, 180 mm fell within three hours; 98 mm in a single hour.
“These cloudbursts and cloudburst-like events were unprecedented,” says Parthasarathi Mukhopadhyay, professor at the Indian Institute of Science Education and Research (IISER), Berhampur. It is not that these events are happening for the first time.
The Mumbai floods of 2005 and the Kerala floods of 2018 are both examples of exceptional convection and rainfall. In the case of 2018 Kerala floods, from August 6 to 19, the state received 150-160 per cent more rainfall than its average for entire month, explains Mukhopadhyay. “But we have not heard about so many such exceptional rainfall events as have occurred in 2025.” Besides, cloudbursts do not feature in any forecasts as an impact of climate change for the plain regions.
Contemporary climate models are still coarse; they inform about general trends over large regions rather than specific events over smaller regions like cloudbursts. “All that we know is for every 1°C rise in average global temperature, water vapour in the atmosphere rises by 7 per cent,” Mukhopadhyay says. “We need to understand the type of convection that can produce such intense rainfall over a small area in such a short time, without the orographic lift from mountains or hills that typically causes cloudbursts in those topographies.”
Despite the gaps in scientific understanding and shortcomings of climate models in capturing the planet’s complex atmospheric churn, recent events point to two clear trends. First, the effects of climate change are showing up in regions that most models did not forecast and are being felt now, much before their forecast periods.
And such disruptions, once thought decades away, are unfolding across the globe—spanning ecosystems and the planet’s physical and climatic systems.
Consider this. On October 16, a landmark report “Global Tipping Points 2025”, produced by 160 scientists from 23 countries, declared that the Earth has reached its first catastrophic climate “tipping point” with the widespread die-off of warm-water coral reefs (see “Collapse of Corals”, 1-15 November, 2025, Down To Earth). A climate tipping point marks the threshold beyond which human-induced warming triggers irreversible planetary changes. Scientists have identified such thresholds, forecasting their breach between the 2030s and the end of the century, depending on emissions scenarios. But as the report shows, it could be happening sooner. “We are in a new climate reality,” says Tim Lenton…
This article was originally published as part of the cover story Earth is warming faster in the November 16-30, 2025 print edition of Down To Earth