The southwest monsoon will hit Kerala on June 6, about five days after the normal date of arrival in mainland India, and it is expected to be sluggish in its progression, the India Meteorological Department (IMD) said on Wednesday.
The forecast comes with a variation of four days.
Private forecaster Skymet on Tuesday said the onset of monsoon would be likely on June 4, with an error margin of two days.
The IMD said its operational forecast about the date of onset of monsoon had proved correct in the past 14 years except in 2015.
"Conditions are becoming favourable for advance of southwest monsoon over the southern part of Andaman Sea, Nicobar Islands and adjoining southeast Bay of Bengal between May 18 and 19," it said.
The monsoon this year is predicted to be "near normal" with around 96% of well-distributed rainfall, the weather office said last month.
The forecast stands at a moderate error estimate of plus-minus 5% of the Long Period Average (LPA) of 887 mm -- the average or normal rainfall in the country defined between 96 and 104% of a 50-year average for the entire four-month monsoon season.