Southwest monsoon has hit the coast of Kerala and advanced into parts of northeast from Thursday, a day ahead of the India Meteorological Department (IMD) forecast.
Earlier, the weather office had announced the onset of monsoon over Kerala by May 31.
Kerala has been receiving heavy rains for the past few days resulting in a surplus May rainfall.
The normal monsoon onset date for Arunachal Pradesh, Tripura, Nagaland, Meghalaya, Mizoram, Manipur, and Assam is June 5.
However, scientists said that Cyclone Remal, which ripped through West Bengal and Bangladesh on Sunday, had pulled the monsoonal flow to the Bay of Bengal, resulting in its early onset over the north-east.
The monsoon is supposed to reach Delhi, which witnessed record-breaking heat on Wednesday, by the end of June. Mahesh Palawat, Vice President of Skymet told NDTV that Delhi is likely to witness monsoon by June 27.
India is likely to receive an average amount of rain in June, although maximum temperatures in the month are likely to remain above normal, according to IMD.
This year's monsoon rains are expected to be 106% of the long-term average.
The IMD defines average or normal rainfall as between 96% and 104% of a 50-year average of 87 cm for the four-month season.
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.
(With agency inputs)
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