Study flags steady drop in Kerala’s southwest, northeast monsoon rainfall

Kerala has reason to worry about increasingly erratic monsoon behaviour, as its average seasonal rainfall during both the southwest and northeast monsoons has shown a steady decline over the past 125 years, according to a report by the Institute for Climate Change Studies (ICCS).

ICCS scientists said that Kerala’s average rainfall during the southwest (June-September) and northeast (October-December) monsoons, the State’s primary sources of precipitation, decreased by 12.5% and 6.1% of the long-period average (LPA, 1971–2020) per 100 years, respectively, between 1901 and 2025.

While the LPA for southwest monsoon rainfall in Kerala is 1,919.3 mm, the LPA for northeast is 478.1 mm.

The information, released as part of the ‘Statement on Climate for the State of Kerala: 2025’, said the average southwest monsoon rainfall during 1901–2025 showed a decreasing trend in all districts except Idukki.

Nine districts, Kottayam, Alappuzha, Kollam, Pathanamthitta, Kannur, Wayanad, Kozhikode, Malappuram, and Palakkad, reported a “significantly decreasing” trend, while Ernakulam, Thrissur, and Kasaragod showed a “decreasing” pattern. In Idukki, an “insignificant increasing” trend was observed.

In the case of the northeast monsoon, decreasing seasonal rainfall was recorded in all districts except Kasaragod, with “significantly decreasing” trends observed in Wayanad, Palakkad, and Kottayam. Kasaragod showed an “insignificant increasing” trend.

“Though climate change is global in nature, its consequences are highly region-specific. The trends we are observing in Kerala highlight how global climate shifts can manifest differently across regions. Given the State’s unique geography, monsoon dependence, and socio-economic structure, even modest long-term changes in rainfall patterns can have significant implications,” said Sinan Nizar, junior scientist, ICCS.

Although the State received 2,925.7 mm of annual rainfall in 2025, a departure of +1.2% from the LPA, officials said the average rainfall during the southwest and northeast monsoons stood at 87% and 79%, respectively, of the LPA.

During the southwest monsoon, three districts, Wayanad (-36%), Idukki (-35%), and Malappuram (-27%), reported significantly below-average rainfall. In contrast, the northeast monsoon was markedly below normal across the State, with eight of the 14 districts recording deficient rainfall. The sharpest deficits were observed in Kollam (-32%) and Malappuram (-33%), followed by Idukki (-26%), Kozhikode (-24%), and Palakkad (-24%).

Despite the long-term decline in average rainfall during both monsoon seasons, Kerala remains prone to extreme precipitation swings. The year 2023 emerged as one of the driest in recent history due to a sharp southwest monsoon deficit, in stark contrast to 2018, which witnessed excess rainfall and devastating floods.