Courtesy Cyclone Ditwah: Rain Deficit Of Tamil Nadu Gets Covered
Key Takeaways
- Tamil Nadu moved from October surplus to November deficit before heavy rains from Cyclone Ditwah restored seasonal rainfall levels.
- Ditwah, after devastating Sri Lanka, weakened and stalled near the Tamil Nadu coast, flooding Chennai for nearly 24 hours.
- The remnant low-pressure system spread rainfall across coastal and interior districts, helping erase most deficits.
- Tamil Nadu now stands at a seasonal surplus of 10%, with Chennai recording a slight surplus as well; light to moderate rain may continue for 2–3 days.
State of Tamil Nadu had received surplus northeast monsoon rains in the month of October. Between 01st and 31st October, the state registered excess rainfall of 36%. However, the chief rainy month of November was drastically sluggish. The surplus of October got consumed, and the state was rain deficit by 10% by the middle of the month. Most districts in the state, including the capital city, were rain-starved in the month of November 2025. Individually, the month recorded a shortfall of 18% rainfall for the state.
Cyclone Ditwah started as a low-pressure area near the Sri Lanka region. The low pressure gradually intensified and developed into a tropical storm, Ditwah. This cyclone travelled through the island nation, Sri Lanka, and literally ravaged it during the last days of November 2025. Later, the storm weakened and entered as a depression over the Southwest Bay of Bengal, off the Tamil Nadu coast.
This was the weather system that pounced very heavy rains over most parts of the state. The depression, as such, took a very nasty track and recurved to move southwestward. The weakened system slowed down terribly in the proximity of North Tamil Nadu, just east abeam Chennai. The capital city was drowned for nearly 24 hours, inflicting loss of life and property.
The remnant of the depression as a low-pressure area continued rainfall activity along the coast of Tamil Nadu and even extended to the interiors like Trichy, Madurai, Thanjavur, Coimbatore, Tirupur, Salem, Karur, Erode and adjoining districts. The northern districts of Kancheepuram and Tiruvallur also had moderate to heavy rainfall. Overall, the state recovered from the large deficit and only a few districts are now having marginal shortfall.
The state of Tamil Nadu has recovered from the deficiency. The rainfall between 01st October and 04th Dec 2025 is break-even for the capital city Chennai. The Chennai district has logged 699.3 mm rainfall against the normal of 691.2 mm so far, recording a surplus of 1%. The state as a whole has registered rainfall of 410.6 mm against the normal of 373 mm, thereby having an excess of 10% seasonal rainfall. The state is expected to have light to moderate rainfall for the next 2–3 days and reduce substantially thereafter.
