Monsoon Onset In Kerala Likely On May 27, Four Days Earlier Than Normal

The southwest monsoon is likely to reach Kerala on May 27, earlier than the usual date of June 1, the India Meteorological Department (IMD) said on Sunday.

If the monsoon arrives in Kerala as expected, it will be the earliest onset over the Indian mainland since 2009, when it began on May 23, according to IMD data.

The arrival of the main rain-bearing system over the Indian mainland is officially declared when it reaches Kerala, usually around June 1.

The monsoon typically covers the entire country by July 8. It starts withdrawing from northwest India around September 17 and completes by October 15.

The monsoon had set in over the southern state on May 30 last year; June 8 in 2023; May 29 in 2022; June 3 in 2021; June 1 in 2020; June 8 in 2019; and May 29 in 2018.

An IMD official said there is no direct relationship between the onset date and the total rainfall over the country during the season.

"The monsoon arriving early or late in Kerala does not mean it will cover other parts of the country accordingly. It is characterised by large-scale variabilities and global, regional and local features," the official said.

The IMD had, in April, forecast above-normal cumulative rainfall in the 2025 monsoon season, ruling out the possibility of El Nino conditions, which are associated with below-normal rainfall in the Indian subcontinent.

"India is likely to see above-normal rainfall in the four-month monsoon season (June to September), with cumulative rainfall estimated at 105 per cent (with a model error of 5 per cent) of the long-period average of 87 cm," M Ravichandran, secretary in the Ministry of Earth Sciences, had said.

According to the IMD, rainfall between 96 per cent and 104 per cent of the 50-year average of 87 cm is considered 'normal'.

Rainfall less than 90 per cent of the long-period average is considered 'deficient'; between 90 per cent and 95 per cent is 'below normal'; between 105 per cent and 110 per cent is 'above normal'; and more than 110 per cent is considered 'excess' precipitation.

The monsoon is crucial for India's agriculture sector, which supports the livelihood of about 42.3 per cent of the population and contributes 18.2 per cent to the country's GDP. It is also vital for replenishing reservoirs critical for drinking water and power generation across the country. 

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