The onset of monsoon could be delayed further by a day to June 7, the India Meteorological Department said on Tuesday.
On Saturday, private weather forecaster Skymet too revised its forecast from June 4 to June 7.
"Cross equatorial flow over southern parts of South Arabian Sea and over the Bay of Bengal is likely to increase gradually favouring further advance of southwest monsoon over some more parts of South Arabian sea, Maldives, Comorin area, southwest, southeast and central Bay of Bengal during next 24 hours," it said.
"An eastwest shear zone at 3.1 kilometres above mean sea level is very likely to develop across extreme south peninsula from tomorrow onwards leading to favourable conditions for onset of southwest monsoon over Kerala during the subsequent 72 hours," it added.
Earth Sciences Minister Harsh Vardhan had also indicated that monsoon could hit the Kerala coast on June 6-7.
Several parts of the country are reeling under severe heat waves with temperatures touching 50 degree Celsius in some parts.
Vardhan said monsoon is likely to be 96 per cent of the Long Period Average (LPA), which falls on the border line of normal and below normal category.