Tamil Nadu’s rainfall picture changes dramatically in 27 days; 18 deficit districts move into normal or excess categories

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Image used for representation | Photo Credit: C. Venkatachalapathy

In a striking shift in Tamil Nadu’s rainfall position, 18 of the 23 districts that were rainfall-deficient at the close of the Southwest monsoon have moved out of the deficit category in the 27 days since October began, Commissioner of Revenue Administration B. Chandra Mohan said on Thursday (October 29, 2026). By October 27, only five districts continued to record deficient cumulative rainfall, while several others had moved into the normal or excess categories.

The change is reflected in the State’s cumulative rainfall figures, he said. “At the end of the Southwest monsoon on September 30, Tamil Nadu had recorded a 16% rainfall deficit. By October 27, the cumulative shortfall had narrowed to less than 1%, bringing the State’s overall rainfall close to its normal level for the period. The shift has been driven by substantial rainfall during the opening weeks of the Northeast monsoon.”

Between October 1 and 27, Tamil Nadu recorded an average of 217.2 mm against the period’s normal of 144.2 mm – a surplus of 51%. All 38 districts received rainfall within the normal, excess or large excess categories during this period, with none recording deficient rainfall during October. The most significant change was evident in districts that had ended September with substantial rainfall shortfalls.

Nagapattinam’s cumulative rainfall departure improved from −54% to −8%, while Karur moved from −53% to −6%. Kallakurichi shifted from −29% to +2% and Erode from −32% to +6%. Mayiladuthurai’s departure narrowed from −28% to −6%, while Tiruchirappalli improved from −39% to −7%. The cumulative rainfall position also improved in the Nilgiris, from −32% to −13%; Namakkal, from −42% to −8%; and Tiruppur, from −40% to +13%.

“These changes illustrate the scale of the shift in just 27 days. Districts that had entered October with marked shortfalls are now recording cumulative rainfall closer to, or above, their respective normals. The improvement is not uniform, however, and some districts continue to carry substantial deficits from earlier months,” Dr. Chandra Mohan said.

The first 27 days of the Northeast monsoon have substantially changed Tamil Nadu’s cumulative rainfall position, with most districts that entered October in deficit now recording rainfall within the normal or excess categories, he said. The Statewide cumulative rainfall deficit has narrowed to less than 1%, reflecting the scale of the improvement so far. With November and December still ahead, the season remains in progress.

“Continued monitoring will be important, particularly in districts where deficits persist and in catchments where rainfall distribution remains uneven. The present figures mark a significant change in the State’s rainfall position, rather than the conclusion of the season’s rainfall needs,” the officer said.

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