Victorians are being urged not to swim at 36 beaches across the state as heavy rainfall is expected to cause poor water quality over the next three days.
The state’s environment watchdog issued the warning on Tuesday as the state braces for two days of downpours.
Water at 36 beaches were rated as poor by the Environment Protection Authority on Tuesday afternoon, with the Port Phillip Bay beaches spread out from the Bellarine Peninsula, across greater Melbourne and along the Mornington Peninsula.
Popular tourist towns such as Queenscliffe, Geelong, Sorrento, Portsea and Mornington will be affected until at least Thursday.
The EPA warned heavy rain that battered the state overnight and into Tuesday morning could flood stormwater systems and then carry pollution built up in drains into waterways.
EPA advised against swimming at all waterways and beaches for up to 48 hours after heavy rain, with a higher risk of illness to swimmers from increased bacterial levels.
It is also advised people prevent their pets from entering the water.
Beachgoers should check the EPA website for latest water quality forecasts as the weather improves over coming days.
A severe weather warning for heavy rainfall and isolated thunderstorms remains in place for southern Victoria with the heaviest falls expected to hit Melbourne on Tuesday evening.
The weather bureau has warned heavy rainfall could lead to flash flooding in parts of western and central Victoria with up to 70mm possible in some areas.
State Emergency Service volunteers have already responded to 91 requests for help across the state in the past 24 hours, including 51 in the central region, which includes Melbourne.