Southwest monsoon hits Kerala, IMD forecasts heavy rainfall until June 7

This year, IMD has forecast below-normal rainfall over the country.

3 min readBengaluruUpdated: Jun 5, 2026 03:40 AM IST

Kerala has been reporting heavy rainfall over the past few days, but the IMD maintains some criteria, all of which, when satisfactorily met, declare the monsoon onset.(Express file photo)

The India Meteorological Department (IMD) Thursday announced the onset of southwest monsoon over Kerala, marking the beginning of the four-month long season.

The normal onset date is June 1, with a deviation of 7 days. This year, the onset has been realised 3 days after the normal date, IMD said.

This year, the Met office has forecast below-normal rainfall over the country. Quantitatively, it is expected to be 90 per cent of the Long Period Average, which is 870mm (1971-2020).

This subdued rainfall forecast is mainly in view of the developing El Nino condition — a global, naturally occurring ocean-atmospheric phenomena along the equatorial Pacific Ocean. El Nino, during which the ocean surface along thePacific is warmer than usual, is known to suppress summer monsoon and drive extreme temperatures over India.

Even though Kerala has been reporting heavy rainfall since last week, the IMD maintains some criteria, all of which when satisfactorily met, declares the monsoon onset over Kerala. These criteria include (i) After May 10, if there is rainfall of 2.5mm or more lasting two consecutive days recorded over stipulated 14 stations within Kerala, Lakshadweep and Karnataka (ii) strengthening and deepening of the westerly winds to 15 – 20 knots and atleast 600 hecta Pascal, respectively and (iii) the Outgoing Long Range (OLR) value (or the heat) remains below 200 watts/sq metre over 5-10ºN latitude and 70-75ºE latitude area.

Once the southwest monsoon sets in over Kerala, it advances northwards in multiple surges depending on the monsoon wind pulses and other factors. Normally, the monsoon covers the entire country by mid-July after which it enters active and break phases from time-to-time. The rainfall activity is closely tracked and is indicated by the Northern Limit of (NLM), an imaginary line to track the monsoon progress across the country. As of Thursday, the NLM passed through Mangalore, Ooty and Kodaikanal having covered most parts of Kerala, whole of Lakshadweep, Mahe and some parts of Karnataka and Tamil Nadu, remaining parts of the Arabian Sea, Comorin area, southeast Bay of Bengal, the IMD said.

The IMD has issued a ‘yellow’ alert warning of the continuing heavy rainfall (70 – 110mm in 24 hours) for all districts of Kerala till June 7.

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The Met office said that favourable conditions prevailed for the monsoon advancement into Goa, some parts of Maharashtra and Andhra Pradesh, more parts of Karnataka, rest of Tamil Nadu, more parts of the Arabian Sea and the Bay of Bengal during the next two-three days.

Onset over Kerala (2015 – 2026)

Year | Onset date
2026 – June 4
2025 – May 24
2024 – May 30
2023 – June 8
2022 – May 29
2021 – June 3
2020 – June 1
2019 – June 8
2018 – May 29
2017 – May 30
2016 – June 8
2015 – June 5

Source : IMD

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