Southwest Monsoon Onset In Kerala: IMD Forecast, Rainfall Outlook And El Nino Impact

Latest assessments by the India Meteorological Department suggest the southwest monsoon will gain proper strength over South India only after June 5–6. This delay means Kerala is likely to see a soft or weak onset rather than a powerful burst, with the full monsoon flow expected to build step by step.

The hesitant start has drawn attention because the southwest monsoon is central to India’s climate and economy. Moist winds from the Indian Ocean deliver most of the country’s rain between June and September. These rains support crops, recharge reservoirs and groundwater, and finally ease the long summer heat for millions of people.

Southwest monsoon IMD forecast and model outlook

At the core of the current outlook is the Global Forecast System, the numerical model run by the India Meteorological Department. This system takes in huge volumes of weather data and simulates how the atmosphere will behave over several days. Its latest charts show strong upper-level easterly winds forming late over southern India.

According to these GFS simulations, a Western Disturbance must first move away from the region. This west-to-east weather system carries moisture and temporarily disturbs the upper air flow. While it lingers, the key easterly winds at higher levels over South India cannot fully organise, so the initial southwest monsoon stream into Kerala remains muted.

Southwest monsoon IMD forecast for Kerala onset conditions

The India Meteorological Department follows clear rules before declaring southwest monsoon onset over Kerala. Officials need to see steady rainfall at at least 60% of selected weather stations, strong enough westerly winds over the Arabian Sea, and adequate cloudiness. Only when all three signals appear together is the formal start date announced.

Currently, clouds and rainfall over Kerala match the required pattern, but the low-level westerly winds are not yet meeting the threshold. Cyclonic activity over the Bay of Bengal earlier weakened the broader monsoon circulation, reducing wind speeds over the Arabian Sea corridor. Experts expect these westerlies to pick up strength from Monday, June 1.

The season has already slipped past the India Meteorological Department’s initial onset window. IMD first projected that the southwest monsoon would reach Kerala around May 26. That estimate has been revised several times, with the latest official guidance suggesting a likely onset during June 2–4, once the necessary weather parameters line up together.

Some parts of Kerala have already experienced pre-monsoon showers, bringing local relief and hinting at the approaching southwest monsoon. However, these early rains alone are not enough for an onset declaration. The department is waiting for a more organised and sustained pattern that fits its rainfall, wind, and cloud cover benchmarks across the wider region.

Southwest monsoon IMD forecast and seasonal rainfall outlook

While the arrival appears close, the bigger concern lies in how strong the overall southwest monsoon may be this year. The India Meteorological Department has already warned that seasonal rainfall across India could stay below normal, as sea surface changes in the Pacific point towards developing El Nino conditions that often reduce monsoon performance.

Initially, the India Meteorological Department projected seasonal rainfall at 92% of the long-period average. Last week, that assessment was revised lower to 90% of the long-period average. The downgrade has raised questions about how much the emerging El Nino pattern might limit a season that underpins food production, hydroelectric supply, and rural incomes.

Large parts of northern and central India are currently under severe heatwave conditions, which raises the stakes for timely southwest monsoon showers. Farmers in these regions are waiting for dependable rains to start sowing key crops such as rice and pulses. Although future model runs may change the outlook, current signs point to a gentle onset and then gradual strengthening.