Widespread rain and thunderstorms are forecast to impact Australia's east coast this week, particularly affecting Queensland and New South Wales.

Residents on the east coast are being warned to prepare for heavy downpours, with a severe weather system expected to bring up to 150mm of rain.

Meteorologist Helen Reid reported forecasted rainfall of 50mm to 70mm north of Coffs Harbour, with localized falls potentially exceeding 120mm.

On Monday, regions in southern Queensland are also expected to receive up to 150mm of rain.

Up to 50mm of rain is anticipated in parts of Queensland, especially on the north tropical coast, with a Flood Watch warning already in effect for South East Queensland.

The Bureau of Meteorology indicated that the north coast of New South Wales would experience the worst of the weather as it moves from Queensland.

In New South Wales, heavy rainfall is expected in the Northern Rivers region, with minor flooding possible in the Tweed, Rous, Wilsons, and Richmond Rivers.

River levels are rising along the Lachlan River at Booligal Weir, with a minor flood peak expected in the coming days.

Flash flooding is a significant concern, particularly in the Northern Rivers region, according to Reid.

Residents are advised that flooding could disrupt transport and isolate some communities.

Marine wind warnings are in effect for coastal regions in Western Australia, South Australia, New South Wales, and Tasmania on Monday.

The severe weather system is expected to move off the coast by Wednesday.