Well, it's official. The much-anticipated northeast monsoon of 2025, which brings the lion's share of rain to Tamil Nadu, has concluded not with a bang, but with a whimper. After five consecutive years of bountiful, above-normal rainfall, the streak has been broken. The final numbers from the India Meteorological Department (IMD) show a combined rainfall of 42. 8 cm for Tamil Nadu and Puducherry, just shy of the 44. 2 cm average—a seemingly small deficit of 3%.
Key Highlights
- ✓ The 2025 northeast monsoon ended with a 3% rainfall deficit for Tamil Nadu and Puducherry.
- ✓ This marks the end of a five-year streak of normal or surplus monsoon rainfall for the state.
- ✓ A strong October (36% above normal) was followed by a very weak November and December.
- ✓ The primary cause was the absence of key weather systems like low-pressure areas in the Bay of Bengal.
- ✓ Despite the deficit, reservoir water levels remain comfortable thanks to the southwest monsoon and early rains.
- ✓ Chennai's five-year run of surplus rainfall has officially come to an end.
But here's the thing about averages—they often hide the real story. This season was a classic tale of two halves, a rollercoaster of early promise followed by a prolonged, frustratingly dry spell. Another important factor is What began with booming, surplus rains in October quickly fizzled out, leaving many of us wondering where the clouds went. Let’s dive into what really happened, why it matters, and what this shift could mean for the region moving forward.
A Roaring Start, A Silent End
If you were in Tamil Nadu during October, you'd be forgiven for thinking another record-breaking monsoon was on the cards. The month was incredibly wet, delivering a whopping 23 cm of rain, which is a massive 36% above the normal for that period. This brings us to The reservoirs were filling up, the ground was saturated, and the general feeling was one of optimism. It seemed like the movement of recent years was set to continue.
Then, November arrived, and the taps seemed to turn off almost overnight. The month limped to a finish with just 15 cm of rain, slightly below its normal of 17 cm. But December was the real shocker. It delivered a paltry 4. 5 cm, a far cry from the usual 9 cm we expect. This sudden and sustained drop-off is what ultimately tipped the scales from a surplus season into a deficit one.
What this tells us is that the timing of rainfall is just as crucial as the total amount. A front-loaded monsoon can secure water storage, which is fantastic news. However, the lack of consistent, widespread rain in the latter half directly impacts agriculture, especially for crops that rely on that late-season moisture. It's a classic case of the final numbers not telling the whole story of the on-ground reality for farmers and local communities.
The Science Behind the Silence
So, what caused this dramatic reversal. According to weather officials and independent bloggers, the main culprits were the large-scale atmospheric patterns over the Indian Ocean. The northeast monsoon doesn't just happen; it needs "drivers"—what meteorologists call favourable synoptic systems. These are essentially the engines of the monsoon, like low-pressure areas and cyclonic circulations that form over the Bay of Bengal and pull moisture-laden clouds over the state. Recent reports indicate that
During November and December of 2025, these systems were conspicuously absent. The Bay of Bengal remained unusually calm. Without these rain-driving engines, the monsoon stalled. Weather bloggers pointed to another major factor: the absence of the Madden-Julian Oscillation (MJO). The MJO is a massive, eastward-moving pulse of clouds and rainfall near the equator that circles the entire globe every 30 to 60 days. When it's in the right phase over the Indian Ocean, it significantly boosts monsoon activity. This year, it was a no-show during the critical period.
An Uneven Spread: A Tale of Two Tamil Nadus
The statewide 3% deficit figure also masks significant variations at the district level. The rain, when it did fall, was not evenly distributed. It created a patchwork of haves and have-nots across the state, which is a major headache for water management and agricultural planning. Some areas did quite well, while others were left high and dry. It's important to highlight
Several districts, including major centers like Chennai, Ariyalur, Chengalpattu, Coimbatore, Dharmapuri, Kancheepuram, Karur, and Tiruchirappalli, recorded below-normal rainfall. This is particularly significant for Chennai, as it officially ends a celebrated five-year streak of surplus rainfall that began back in 2020. This shift might require a re-evaluation of the city's water management strategies, which had become accustomed to abundance.
On the flip side, it wasn't all unsatisfactory news. A handful of districts, mostly in the south and west, managed to buck the movement. Virudhunagar, Vellore, Thoothukudi, Tiruvarur, Tirunelveli, and Tenkasi all received surplus rainfall. Recent reports indicate that This geographic disparity is the real story of the 2025 monsoon—a reminder that a single average number can never capture the diverse experiences across a large and geographically varied state like Tamil Nadu.
The Bigger Picture Across the Southern Peninsula
To truly understand this year's monsoon, we need to zoom out and look at the whole of South India. What's fascinating is that while Tamil Nadu experienced a deficit, other regions had a completely different story. The weather systems that failed to materialize for Tamil Nadu's coast seem to have favored inland areas. This provides crucial context for the atmospheric patterns at play.
For instance, Telangana received a massive 45% excess in rainfall, while neighboring Rayalaseema saw a 34% surplus. This suggests the moisture and systems tracked further north and inland than usual. This is a significant deviation from typical northeast monsoon patterns. You can find more about these weather systems on the official India Meteorological Department (IMD) website, which tracks these developments closely.
Meanwhile, other regions struggled alongside Tamil Nadu. Kerala and Mahe ended the season with a significant 21% deficit. But the worst-hit area was North Interior Karnataka, which suffered a severe deficit of 32%. This broader view shows that the 2025 northeast monsoon wasn't just weak; it was erratic and highly selective in its generosity, reshaping the hydrological map of the entire southern peninsula for the season.
A Silver Lining and a Chilly Forecast
Now for the good news. Despite the monsoon's subpar performance, officials have stated that the state's water storage levels are "comfortable. " This is the crucial silver lining in an otherwise cloudy story. The buffer we have is thanks to two key factors: a healthy southwest monsoon earlier in the year and that incredibly wet October, which topped up the reservoirs just in time.
This means that, for the near term, drinking water and irrigation needs should be met without major issues. It’s a testament to the importance of year-round water management and not just relying on one monsoon season. Looking ahead, there's a glimmer of hope for some late showers. Weather models from the European Centre for Medium-Range Weather Forecasts (ECMWF) indicate an easterly wave could bring scattered rainfall to southern Tamil Nadu and Kerala as we head into the first week of the New Year.
In the meantime, the dominance of dry, high-pressure systems has ushered in a different kind of weather: a cold spell. Minimum temperatures are expected to drop across the state, and a ground frost warning has even been issued for the higher ranges of Kodaikanal and the Nilgiris district. It's a stark reminder that the absence of rain often brings its own set of distinct weather challenges.
What This Shift Means for the Future
From my perspective, the end of the five-year surplus streak is more than just a statistic; it's a significant reset. It serves as a crucial reminder that we can't take bountiful monsoons for granted. Climate is inherently variable, and after a period of relative stability and abundance, this year reintroduces a level of unpredictability that water managers, farmers, and the public need to be prepared for.
The reliance on phenomena like the Madden-Julian Oscillation highlights our vulnerability to large-scale climate patterns that are far beyond our control. As these global patterns potentially become more erratic, our local weather will follow suit. One key aspect to consider is This season underscores the importance of diversifying water sources, investing in water conservation, and creating more resilient agricultural practices. The "comfortable" reservoir levels bought us time this year, but the 2025 monsoon is a clear warning shot for the future.
Conclusion
To sum it up, the 2025 northeast monsoon for Tamil Nadu was a complex and ultimately underwhelming season. It was a story of a powerful start completely undermined by a weak finish, driven by the absence of critical weather systems in the Bay of Bengal. The final 3% deficit breaks a five-year surplus streak and reminds us of the monsoon's inherent unpredictability.
While the comfortable reservoir levels provide a crucial cushion for now, the uneven rainfall distribution and the end of Chennai's surplus run are significant developments. This season serves as a valuable lesson in resilience and a prompt to reinforce water conservation efforts. After years of plenty, 2025 is the year the monsoon reminded us it always has the final say.
About the Author
This article was written by the editorial team at ChopalCharcha, dedicated to bringing you the latest news, trends, and insights across entertainment, lifestyle, sports, and more.
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