Northeast Monsoon (NEM) rainfall not exactly an outlook, just a glimpse what can be expected in 2026. ----------------------- El Niño is an important factor, but it does not determine the outcome of the Northeast Monsoon. The monsoon has its own way of unfolding, often throwing surprises and reminding us that every season has a story of its own For reference, the seasonal NEM rainfall normal is 855 mm for Chennai and 445 mm for Tamil Nadu. Interestingly, historical comparisons suggest that around 85–90% of El Niño years have recorded above normal NEM rainfall. This is a historical tendency, not a guarantee of what any particular year will deliver. A look back at some remarkable years ------------- 2015: Chennai recorded around 1,664 mm during the Northeast Monsoon, a season remembered for its catastrophic floods. 1997: Tamil Nadu recorded around 810 mm, setting a remarkable rainfall record that surpassed the previous benchmark from 1946. 1982: A contrasting year, with significant rainfall deficits across Chennai and Tamil Nadu. One striking aspect of 1997 and 2015 is that their extraordinary rainfall outcomes were not simply a consequence of frequent cyclone activity. In particular, 1997 stands out for the scale of rainfall recorded across Tamil Nadu despite the relative lack of cyclonic activity. What about the 2026 Northeast Monsoon? ------------------------- The 2026 Pacific sea-surface temperature pattern shows a strong warm signal along the equatorial Pacific, consistent with El Niño conditions. However, history reminds us that we cannot assess the Northeast Monsoon by looking at El Niño alone. The Indian Ocean Dipole (IOD) is another important player, influencing the broader ocean-atmosphere environment. And then comes the kingmaker the Madden–Julian Oscillation (MJO). King maker MJO -------------- The MJO's presence over our basin during the past week is encouraging and we can see the Tamil Nadu rains this october from negative to positive with MJO's help . If it remains favourable and spends a meaningful amount of time over the Indian Ocean during November, it could support active spells of convection and rainfall over Tamil Nadu. Its movement and persistence will be crucial factors to watch. My rainfall outlook for 2026 ----------------------------- Tamil Nadu: The season has the potential to finish above normal, possibly in the 470–520 mm range, compared with the normal of 445 mm. Chennai (KTCC): Against a normal of 855 mm, the city has received approximately 230 mm so far. The coming days could help push the seasonal total towards or beyond 300 mm, depending on how the last week Low pressure play out, if it goes to North Andhra / Odisha, we might miss crucial spells. 1. Tamil Nadu, I do not expect 2026 to match the extraordinary rainfall totals of 2015, let alone approach the 1997 benchmark of 810 mm. A finish closer to 500 mm looks like a reasonable possibility at this stage. 2. KTCC (Chennai), however, the story could be different. A few intense, well-positioned rainfall events can dramatically change the seasonal tally. Crossing 1,000 mm is possible, although it would require favourable conditions to persist and some significant rainfall spells. Reaching the exceptional levels of 1,500 mm or more recorded in years such as 2015 and 1997 would be a much bigger challenge. 3. . South Tamil Nadu — El Niño years, South TN oda attam vera level!. Districts such as Kanyakumari, Tirunelveli, Theni, Tenkasi, Virudhunagar, Thoothukudi, Madurai and Ramanathapuram can perform very well during El Niño years, with several areas having the potential to record high excess rainfall. South Tamil Nadu is one of the regions I am optimistic about this season. 4.. West Tamil Nadu — The Kongu belt's only concern. Districts such as Coimbatore, the Nilgiris and other parts of the Kongu belt depend significantly on low-pressure areas and upper-air cyclonic circulations (UACs) moving from the Bay of Bengal across the peninsula towards the Arabian Sea. These systems can bring very good rainfall to the western districts. So watchout for +IOD which can lead to more systems in Arabian sea, which can help easterlies to Kongu belt. This region remains my main area of concern. However, years such as 1997 showed that the Kongu belt can perform exceptionally well. These districts have already started October with a bang, and I expect them to do well during the October 20–24 spell. Normal to slightly above-normal rainfall is a reasonable expectation for this region. 5. Interior Tamil Nadu — Many UACs could make the difference. From Salem, Dharmapuri, Krishnagiri and Tirupattur to Vellore, Kallakurichi, Tiruvannamalai and other interior districts, rainfall often depends on the formation and movement of upper-air cyclonic circulations or weak ciruclations. Such systems are not uncommon during El Niño years. These districts, along with the Kongu belt, bore the brunt of hot spells and relatively poor rainfall during the Southwest Monsoon. However, the Northeast Monsoon offers a fresh opportunity. I expect most of these interior districts to receive normal to above-normal rainfall during NEM 2026, provided favourable circulations develop. 6. Delta and Cuddalore–Puducherry belt — The wettest zone of NEM!. From Cuddalore through the Delta districts towards Puducherry, this belt is among the most favoured regions during the Northeast Monsoon. No major surprises here I expect this region to perform very well, with the potential for at least 20% excess rainfall over the seasonal normal. The Northeast Monsoon still has a long way to go. November, in particular, could be decisive. November forecast is looking good. As always, these are my current expectations based on the evolving climate and weather pattern, not a certainty as always NEM throws few surprises along the way and rains tell their own story.