Southwest Monsoon has set in over Kerala and advanced into most parts of northeast, including Nagaland, Manipur, Mizoram, Arunachal Pradesh and most parts of Tripura, Meghalaya and Assam on Thursday, the India Meteorological Department (IMD) said.

The Southwest Monsoon normally sets in over Kerala on June 1 with a standard deviation of about seven days.

Monsoon is crucial, especially for kharif crops, which are dependent on rains. India has three cropping seasons — summer, kharif and rabi.

The onset of the monsoon in Kerala marks the start of India’s southwest monsoon season, which stretches from June to September, and accounts for over 70 per cent of the country’s annual rainfall.

The influence of Cyclone Remal is reported to have accelerated the onset of monsoon over the northeast as well.

“The Southwest Monsoon has advanced into remaining parts of southwest Arabian Sea, some parts of west central Arabian Sea, most parts southeast Arabian Sea and Lakshadweep area, most parts of Kerala, Mahe, some parts of south Tamil Nadu, remaining parts of Maldives and Comorin area; some more parts northeast Bay of Bengal, most parts of northeast India including entire Nagaland, Manipur, Mizoram, Arunachal Pradesh and most parts of Tripura, Meghalaya and Assam,” the IMD said on Thursday.

“Thus, Southwest Monsoon has set in over Kerala, today on 30th May, 2024,” the IMD said.

Conditions are favourable for further advance of Southwest Monsoon into some more parts of central Arabian Sea, remaining parts of south Arabian Sea, Lakshadweep area and Kerala, some parts of Karnataka, Some more parts of Tamil Nadu, Southwest & Central Bay of Bengal, remaining parts of Northeast Bay of Bengal and Assam and Meghalaya and some parts of Sub-Himalayan West Bengal and Sikkim during next 2-3 days.

IMD had said on Wednesday that conditions were rapidly becoming favourable for the onset of the southwest monsoon over Kerala within the next 24 hours. This was a day earlier than IMD’s first forecast for the onset of the monsoon on May 31.

Normally, the monsoon arrives in the northeastern states of Arunachal Pradesh, Tripura, Nagaland, Meghalaya, Mizoram, Manipur, and Assam on June 5.

Earlier on May 27, the IMD updated its Long-Range Forecast Outlook for the Southwest Monsoon Rainfall Season (June–September) 2024.

The IMD said, “Quantitatively, the southwest monsoon seasonal rainfall over the country as a whole is likely to be 106% of the long period average (LPA) with a model error of ± 4%. Thus, Above Normal rainfall is most likely over the country as a whole during the monsoon season (June to September), 2024.”

The onset of the monsoon in Kerala marks the start of India’s southwest monsoon season, which stretches from June to September, and accounts for over 70 per cent of the country’s annual rainfall.

The monsoon plays a key role in the Indian economy as close to 50 per cent of the country’s farmland does not have any other source of irrigation. The monsoon rains are also crucial for recharging the country’s reservoirs and aquifers from which the water can be used later in the year to irrigate crops.

The advance of the southwest monsoon over the Indian mainland is marked by monsoon onset over Kerala and is an important indicator characterising the transition from a hot and dry season to a rainy season.

As the monsoon progresses northward, relief from scorching summer temperatures is experienced over the areas that it tends to cover.

These rains are crucial to the Indian agriculture economy (especially for kharif crops). India has three cropping seasons — summer, kharif and rabi.

Crops that are sown during October and November and the produce harvested from January depending on maturity are Rabi. Crops sown during June-July and dependent on monsoon rains are harvested in October-November are kharif. Crops produced between Rabi and Kharif are Summer crops.

Traditionally, the Kharif crops are heavily dependent on the normal progression of monsoon rainfall. Paddy, moong, Bajra, maize, groundnut, soya bean, and cotton are some of the major Kharif crops.

The dependency of Kharif crop output on monsoon rainfall has been on a gradual decline, according to an analysis done by India Ratings and Research (Ind-Ra).