Seasonal Rainfall
Patterns in Tamil Nadu
The Tamil month of Thai (approximately mid-January to mid-February) falls within the winter season, following the Northeast monsoon (October-December). According to data from the India Meteorological Department (IMD), this period is typically the driest in the state. Long-term normals indicate very low rainfall, with January and February often recording totals of around 10-30 mm combined for many regions.
For Tamil Nadu as a whole, the normal winter season rainfall (January-February) is approximately 12-13 mm. The Cauvery Delta districts (such as Thanjavur, Tiruvarur, Nagapattinam, and Trichy) and southern districts (including Madurai, Tirunelveli, and Theni) receive minimal precipitation during this time, often less than 15 mm per month on average. This dry phase supports the maturation and harvesting of key crops, particularly paddy varieties like samba and thaladi in the delta region, which is Tamil Nadu’s primary rice-producing area.
Observed Rainfall in Early 2026 Winter Season
As of early February 2026, IMD data shows that the winter season rainfall (from January 1 to February 1) for Tamil Nadu and Puducherry reached 33.2-33.4 mm, compared to a normal of about 12.4-12.5 mm. This represents a significant excess of around 167% departure from normal.
Daily and district-level reports indicate isolated to scattered light to moderate rainfall in parts of the delta and southern districts, with some areas recording measurable amounts even in early February. While nationwide January rainfall was below normal (31.5% deficit for India overall), the South Peninsular region, including Tamil Nadu, saw near-normal to slightly above-normal conditions at about 10.9% excess in January.
These figures highlight that the accumulated rainfall in the initial part of the winter season has been markedly higher than the climatological average, driven by occasional systems affecting the region post-Northeast monsoon withdrawal.
Reasons This Rainfall Is Unusual
The winter months in Tamil Nadu are characterized by dry northeasterly winds and minimal moisture incursion, making widespread or persistent rain rare. IMD climatological records confirm that January-February is among the lowest rainfall periods, with normals reflecting this arid pattern essential for post-monsoon agriculture.
Excess rainfall in this season, such as the observed 167% departure in early 2026, deviates substantially from these established norms. Such anomalies can stem from lingering low-pressure influences or other synoptic features extending from the monsoon transition, though they are not the typical expectation for Thai. This irregularity disrupts the predictable dry window that farmers rely on for crop ripening and harvest.
Impacts on Agriculture in Delta and Southern Districts
In the Cauvery Delta, paddy crops are often in critical stages—maturing or ready for harvest—during Thai. Excess or unseasonal moisture leads to adverse effects:
Waterlogging in fields causes grain sprouting, rotting, and quality deterioration.
Elevated humidity promotes fungal diseases and pest proliferation.
Delayed or disrupted harvesting reduces yields and market value.
Southern districts, with rainfed or irrigated crops like pulses and groundnuts, face similar risks from disrupted growth cycles. While light isolated showers may have limited impact, the accumulated excess observed in 2026 increases the potential for these issues, particularly in low-lying delta areas prone to flooding.
Dry conditions are preferred during this period to ensure proper grain filling and safe harvesting. Any notable deviation toward wetter weather generally does not favor optimal crop outcomes and can contribute to losses.
Broader Context and Outlook
IMD forecasts indicate that February 2026 rainfall over India as a whole is likely to be below normal (less than 81% of the long-period average), with similar expectations for most parts of the country, including southern regions. This suggests a potential return to drier conditions, which would benefit ongoing agricultural activities if realized.
However, the early-season excess already experienced underscores vulnerabilities in rain-dependent farming. Adaptive measures, such as improved field drainage and selection of resilient varieties, remain important for mitigating such climatic variations.
In conclusion, the rainfall during the early Thai month in 2026 has been unusually high compared to IMD normals, marking a clear departure from the typical dry winter pattern. This does not augur well for crops in the delta and southern Tamil Nadu, where excess moisture poses risks to standing paddy and other harvests at sensitive stages. Monitoring evolving conditions will be key for farmers navigating this anomaly.