PIB TrackerIMD forecasts a below-normal 2026 monsoon
The India Meteorological Department's first-stage long-range forecast puts June–September rainfall at 92% of the long-period average — the "below normal" band — with the odds of a deficient season more than doubling against climatology.
What happened
- The India Meteorological Department (IMD), the national weather service under the Ministry of Earth Sciences, released its first-stage Long Range Forecast (LRF) for the 2026 southwest monsoon on 13 April 2026.
- Seasonal (June–September) rainfall over the country as a whole is most likely to be below normal, quantified at 92% of the Long Period Average (LPA) with a model error of ±5%.
- The reference LPA, computed on the 1971–2020 base period, is 87 cm of seasonal rainfall for the country.
- The probability forecast puts a 35% chance of a deficient season (against a 16% climatological baseline) and a 31% chance of below-normal rainfall (against 17%) — both well above their long-run averages.
- Below-normal rainfall is judged most likely over many parts of the country, except some areas over Northeast India, Northwest India, and the South Peninsula.
- IMD attributed the outlook to a weak La Niña transitioning to ENSO-neutral, with its coupled model hinting at El Niño developing within the season, alongside a neutral Indian Ocean Dipole and below-normal Northern Hemisphere snow cover.
- A second-stage updated forecast is due in the last week of May 2026, refining the all-India outlook and adding month-wise and regional detail.
Background & context
The southwest monsoon is the four-month rain-bearing system (broadly June to September) that delivers roughly three-quarters of India's annual rainfall and underwrites the Kharif cropping season, reservoir storage, hydropower and groundwater recharge. Because so much of the agrarian economy and the year's water budget hinge on it, an early read on the season carries real planning weight — which is why IMD's April forecast is one of the most closely watched scientific statements of the Indian calendar.
IMD has issued an operational two-stage long-range forecast since 2003: a first stage in April giving the all-India seasonal outlook, and an update by the end of May that revises the all-India figure and adds spatial and monthly detail. The forecasting approach itself was overhauled in 2021, when IMD moved to a strategy combining statistical and dynamical models — a Multi-Model Ensemble (MME) built on coupled global climate models, including IMD's own Monsoon Mission Climate Forecast System (MMCFS). The MMCFS is the dynamical engine developed under the Monsoon Mission, a Ministry of Earth Sciences initiative to build an indigenous seasonal-prediction capability rather than depend wholly on statistical regression on past data.
The "Long Period Average" is the anchor of the whole exercise. It is the mean of seasonal rainfall over a long reference window, and IMD periodically updates that window so the baseline keeps pace with the evolving climate. The current LPA of 87 cm rests on the 1971–2020 data, replacing the earlier 1961–2010 figure of about 88 cm. A forecast is always expressed as a percentage of this LPA, never as an absolute centimetre figure handed to the public, because the percentage immediately tells an aspirant or a planner where the season sits relative to "normal."
For Prelims
- Issuing body: India Meteorological Department (IMD), founded 1875, headquartered in New Delhi, under the Ministry of Earth Sciences; it is the nodal agency for meteorological observations, weather forecasting and seismology in India.
- Forecast headline: 2026 southwest monsoon rainfall = 92% of LPA ±5% → "below normal."
- LPA: 87 cm, on the 1971–2020 base period.
- Two-stage LRF since 2003: first stage in April, update by end of May (here, last week of May 2026).
- Method (since 2021): combined statistical + dynamical Multi-Model Ensemble, including IMD's MMCFS coupled climate model.
- Key drivers cited: weak La Niña → ENSO-neutral (model hints El Niño in-season); neutral IOD turning positive late-season; below-normal Northern Hemisphere snow cover (Jan–Mar).
The five rainfall categories — the most question-prone table. IMD classifies all-India seasonal rainfall into five bands defined as a percentage of LPA. The 2026 first-stage forecast assigns each a probability, set against its long-run climatological frequency:
| Category | Range (% of LPA) | Forecast % | Climatology % |
|---|---|---|---|
| Deficient | below 90 | 35 | 16 |
| Below Normal | 90–95 | 31 | 17 |
| Normal | 96–104 | 27 | 33 |
| Above Normal | 105–110 | 6 | 16 |
| Excess | above 110 | 1 | 17 |
Read the table the way an examiner does: the forecast loads probability onto the dry end of the distribution. The Deficient and Below-Normal bands together carry 66% of the forecast probability, against a climatological 33% — the season's odds of a dry outturn are roughly double the historical baseline. At 92% of LPA, the central estimate itself sits squarely in the Below-Normal band (90–95%).
The drivers, decoded. Three large-scale signals shape an Indian monsoon forecast, and all three appear in this release. The El Niño–Southern Oscillation (ENSO) is the Pacific Ocean see-saw: El Niño (a warm eastern-Pacific phase) is statistically associated with weaker Indian monsoons, La Niña (the cool phase) with stronger ones, and the present "weak La Niña fading to neutral, with El Niño possibly developing in-season" is a tilt away from the favourable phase. The Indian Ocean Dipole (IOD) is the analogous east–west temperature gradient across the tropical Indian Ocean: a positive IOD generally aids the monsoon, and IMD expects neutral conditions now turning positive late in the season. The third signal is Northern Hemisphere snow cover — Eurasian winter and spring snow shares an inverse relationship with the following monsoon (more snow tends to mean a weaker monsoon), so the slightly below-normal Jan–Mar 2026 cover is a marginally favourable hand against the unfavourable ENSO tilt.
Why it matters
A below-normal April forecast is a planning input long before a single raindrop falls. It feeds early decisions on crop choice and sowing — nudging farmers and State agriculture departments toward shorter-duration, drought-tolerant and less water-intensive varieties — and shapes how reservoir managers, the power sector and urban water utilities phase their drawdown through the lean months. Because the southwest monsoon supplies the bulk of the water for the Kharif season, a dry tilt feeds straight into food-grain output projections, pulse and oilseed availability, rural wages and, ultimately, food inflation and the broader price level the Reserve Bank watches.
The forecast also addresses a structural vulnerability: a large share of India's net sown area remains rain-fed and therefore exposed to monsoon variability, so an early, quantified seasonal signal — even a probabilistic one — buys the State machinery weeks to pre-position contingency seed, fodder reserves and employment-guarantee works before stress sets in. The honest framing in the release — a central estimate with an explicit error bar and an acknowledged regional spread — also models good scientific communication: it gives planners a usable expectation without overselling a single deterministic number.
The forecast deliberately keeps two questions apart: how much rain the season delivers, and how that rain is distributed in time and space. The April figure speaks only to the all-India seasonal total. A season can hit "below normal" overall yet still ruin a crop through bad timing — a long dry spell during sowing or grain-filling — or, conversely, soften a low total with well-spaced rain. That is exactly why the end-of-May second stage adds monthly and regional break-ups, and why month-by-month and even shorter sub-seasonal forecasts matter more to a farmer than the headline percentage. The spatial caveat in this release — that the dry tilt spares parts of the Northeast, Northwest and South Peninsula — is the first hint of that variation.