India Meteorological Department (IMD) has issued its first stage Long-Range Forecast (LRF) for the Southwest Monsoon Season (June–September) 2026, predicting below normal rainfall over most parts of the country.
Key Forecast
- Quantitative forecast– Monsoon seasonal rainfall likely to be 92% of the Long Period Average (LPA) with a model error of ±5%
- LPA for seasonal rainfall (1971–2020)- 87 cm
- Most likely category– Below Normal (90–95% of LPA)
Five-Category Probability Forecast
- Deficient (<90% LPA)– Forecast probability 35% vs climatological 16%
- Below Normal (90–95%)– 31% vs 17%
- Normal (96–104%)– 27% vs 33%
- Above Normal (105–110%)– 6% vs 16%
- Excess (>110%)– 1% vs 17%
Probabilities for below normal and deficient categories are significantly higher than climatological norms, while above normal and excess categories are much lower.
Spatial Distribution
- Below-normal rainfall most likely over many parts of the country
- Normal to above-normal rainfall likely over some areas of Northeast, Northwest and South Peninsular India
Key Influencing Factors
ENSO Conditions (Pacific Ocean):
- Currently weak La Niña-like conditions transitioning to ENSO-neutral
- MMCFS forecasts suggest possible development of El Niño conditions during the SW Monsoon season- a potential negative factor for Indian monsoon
Indian Ocean Dipole (IOD):
- Currently neutral IOD conditions
- Positive IOD conditions likely to develop towards end of monsoon season- which generally has a favourable influence on Indian rainfall
Northern Hemisphere Snow Cover:
- Snow cover extent during January–March 2026 was slightly below normal
- Below-normal snow cover generally has an inverse relationship with monsoon rainfall- indicating a positive signal for rainfall
What is IMD’s Long-Range Forecast (LRF) Strategy?
- IMD has been issuing operational Long-Range Forecasts for SW Monsoon since 2003 in two stages.
- Stage 1: issued in April- Consists of:
- Quantitative and probabilistic forecasts for the country as a whole
- Spatial distribution of probabilistic forecasts for the tercile categories (above normal, normal, and below normal) of the seasonal (June-September) rainfall over the country.
- Stage 2: issued end of May- Consist of:
- Update for the seasonal rainfall forecast issued in April
- Probabilistic forecasts for the seasonal rainfall over the four homogenous regions of India (northwest India, central India, south Peninsula, and northeast India) and monsoon core zone (MCZ).
- Uses Multi-Model Ensemble (MME) forecasting system based on coupled global climate models (CGCMs) from different global climate prediction centres, including IMD’s Monsoon Mission Climate Forecast System (MMCFS) are used in dynamical forecast system.