Heavy downpours, storms and possible flash flooding are set to batter Australia’s south-east.

A band of widespread rain and thunderstorms is sweeping across NSW, Victoria, Tasmania and border regions in Queensland.

Days of heavy downpours have polluted dozens of beaches along Melbourne’s Port Phillip Bay, while rain is forecast to increase across eastern NSW and south-east Queensland later in the week.

The Bureau of Meteorology’s Dean Narramore said thunderstorms would develop in southern and south-eastern Queensland on Wednesday with rain increasing across the NSW coast and further south.

A cold front is also expected to spread into southern Queensland and northern NSW, spreading statewide by Friday.

“Rain and thunderstorms will intensify throughout the week with possible flash flooding, strong winds and widespread heavy rain,” he said.

The NSW State Emergency Service also anticipates a flurry of requests for help as the trough moves through the state.

Wet weather will track along the east coast.

Communities in the New England and Northern Rivers regions, and along the northern half of the mid-north coast, should expect widespread showers of 30-50 millimetres and up to 100 millimetres in some areas.

The bureau is forecasting the trough will deepen on Friday and potentially develop into a low-end east-coast low, impacting the NSW mid-north coast before shifting to the Hunter, Sydney, Blue Mountains and Illawarra by the evening.

“That may bring damaging winds, heavy rainfall and dangerous surf to much of the coastal area,” meteorologist Sarah Scully said.

The weather system is expected to move south on Saturday to the Illawarra and NSW south coast, bringing heavy rainfall, strong to gale-force winds and hazardous surf.

NSW SES assistant commissioner Sean Keans urged east coast, Blue Mountains and metropolitan Sydney communities to prepare for poor weather by cleaning gutters, trimming trees and branches and securing loose items around homes.

“We still have a few days until the weather may deteriorate, so it’s a good time to make sure you take steps to prepare your homes,” he said.

Emergency assets and crews have been pre-positioned ahead of the forecasted wild weather, Keans said.

“Flood and storms teams are on standby to respond should they be required, but we’re pleading with the community to be prepared, stay informed and not drive through floodwaters.”

The warning comes after Melbourne was hit by the equivalent of a month’s rain on Monday. Some parts of Victoria had rainfall not seen for more than 150 years.

– AAP