"The southwest monsoon has set in over Kerala today (Saturday)," said L.S. Rathore, director general of the IMD.
"The rainfall monitoring stations for the monsoon's onset over Kerala have reported fairly widespread to widespread rainfall in the last 48 hours," he said.
According to IMD, the monsoon has covered all of Kerala, some parts of coastal and south interior Karnataka, most parts of Tamil Nadu and some more parts of southwest and westcentral Bay of Bengal.
"Conditions are favourable for further advance of monsoon into some more parts of the central Arabian Sea and Karnataka, remaining parts of Tamil Nadu, some parts of south Andhra Pradesh and some more parts of Bay of Bengal during next 48 hours," Rathore said.
The southwest monsoon normally sets in over Kerala around June 1, and advances northwards, usually in surges, covering the entire country by mid-July.