A severe weather event which will bring with it a month's worth of rain in just a matter of days is set to lash Australia's east coast.
The wet weather will stretch from Queensland to Tasmania, bringing unusual May falls to inland parts of New South Wales and Queensland.
Parts of Queensland affected by Cyclone Debbie just over a month ago are set to be hit hardest with up to 200 millimetres of rainfall expected in the north over the next three days.
The Bureau of Meteorology (BOM) has issued an initial flood watch for Queensland coastal catchments from Cairns to Gladstone, including Townsville, Mackay and Rockhampton, extending inland to include parts of the Burdekin and Fitzroy catchments.
"River levels have returned to normal after the rain brought by Cyclone Debbie, however the dam levels are currently high where some of the heaviest rainfall totals are expected in coming days," said BOM forecaster Lauren Pattie.
"The Burdekin river catchment, Eungella dam and the Teemburra dam in the Pioneer region are the ones to keep a close eye on."
BOM said widespread rainfall totals of 100mm to 200mm were forecast to occur across the watch area from Wednesday evening through to Friday evening.
Rain and isolated storms are expected in southeast coastal districts including Brisbane on Friday, with decreasing rainfall in the 25 to 75mm range, and isolated showers and storms could continue on Saturday.
Victoria, Tasmania in path of Big Wet
BOM senior meteorologist Scott Williams said smaller rain totals were also expected in areas of New South Wales and Victoria from Thursday, and in Tasmania from Saturday.
"It's unusual to get a band [of rain] that extends right across the country this late, outside the traditional wet season," Mr Williams said.
In Victoria, the most significant rainfall is expected to fall in the western part of the state beginning on Thursday night into Friday, with falls ranging from 30 to 50mm across the Mallee, Northern Country and Wimmera.
Thunderstorms are possible across the north-west late on Thursday, potentially bringing localised heavier falls.
"We expect 10 to 20mm of rainfall across the south-west during the same period and rain will spread to central areas during Friday, with 5 to 15 mm forecast in the Melbourne region before clearing on Saturday," Mr Williams added.
"Northern Tasmania on Saturday looks set to get 30 to 50 mm. There could be some falls there that get to 80 to 100, particularly about the higher ranges."
The Bureau expects to issue a Flood Watch for all northern Tasmanian river basins from Thursday.