"Monsoon arrived in most parts of West Bengal today, while it has become active in some parts Odisha, Jharkhand and Bihar," regional Met director G C Debnath said here.
"As a result, rainfall will be fairly widespread over all districts of West Bengal," he said.
Though the monsoon sets its foot in Gangetic West Bengal on June 10, it arrived eight days late this year.
He said from June 20 onwards, heavy rainfall would occur in the Terai region of Darjeeling, Coochbehar and Jalpaiguri districts.
Heatwave conditions prevailed in many parts of the western districts of the state, including Purulia, Birbhum, Bankura and West Midnapore. These areas are likely to get relief from the hot and dry conditions with the onset of monsoons.