Southwest monsoon, the lifeline of India's farm-based economy, on Sunday made its onset over the Nicobar Islands, the southernmost region of the country, the India Meteorological Department (IMD) said here.

"Southwest monsoon has advanced into some parts of the Maldives, and the Comorin area and some parts of the South Bay of Bengal, Nicobar Islands and South Andaman Sea on Sunday," the weather office said.

The annual rainfall phenomenon is expected to reach Kerala by May 31.

The date of monsoon onset over Kerala has varied widely over the last 150 years, the earliest being May 11 in 1918, and the most delayed being June 18 in 1972, according to IMD data.

The rain-bearing system arrived in the southern state on June 8 last year, May 29 in 2022, June 3 in 2021 and June 1 in 2020.

Last month, the IMD had forecast above-normal rain in the monsoon season in India with favourable La Nina conditions, cooling of equatorial Pacific Ocean, expected to set in by August-September. La Nina conditions help in a good monsoon season over India.

Large parts of the country are battling a brutal heatwave with maximum temperatures touching 48 degrees Celsius, shattering records in several states and severely impacting health and livelihoods. Southern India experienced heatwave spells in April.

The crippling heat is straining power grids and drying up water bodies triggering drought-like conditions in parts of the country. A prediction of above-normal monsoonal rainfall, therefore, comes as a huge relief to the fast-developing South Asian nation.

The monsoon is critical for India's agricultural landscape, with 52 per cent of the net cultivated area relying on it. It is also crucial for replenishing reservoirs critical for drinking water, apart from power generation across the country.

June and July are considered the most important monsoon months for agriculture because most of the sowing for the kharif crop takes place during this period.

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