Heavy to very heavy rainfall is likely to occur in Konkan and central Maharashtra over the next four to five days, the India Meteorological Department has said.

Mumbai and neighbouring Thane are likely to witness maximum rainfall intensity on Friday and Saturday, when the Ganesh festival commences, IMD Mumbai centre’s deputy director general K.S. Hosalikar said.

The 10-day Ganesh festival will begin on August 22.

“With likely formation of low pressure ovr N Bay on 19Aug & getting well marked in nxt 24hrs & moving westwards;Mah,Goa,Guj likely to receive widespread RF nxt 4-5 days with hvy to very hvy RF ovr Konkan, M Mah more:Mumbai Thane too. 21-22 could be Max;Arrival days of Lord Ganesha,” Mr. Hosalikar tweeted late Tuesday night.

The Modak Sagar dam, one of the seven reservoirs which supply water to Mumbai, started overflowing on Tuesday night following incessant rains in its catchment area, a civic official said.

With good rainfall this month, the seven dams- Bhatsa, Upper Vaitarna, Middle Vaitarna, Tansa, Modak Sagar, Vihar and Tulsi - have 83 per cent water stock, officials said.