HEAVY rain will soak much of Queensland over the next three days as two separate weather systems hit the state, sparking fears of widespread flooding.
A month's worth of rain is expected to fall on some regions, prompting the weather bureau to issue a flood watch for residents from Tully to as far south as Cunnamulla.
The Whitsundays - still reeling from the damage of Cyclone Debbie - will receive the heaviest of the deluge today, with the weather bureau forecasting possible falls of up to 200mm.
Near-capacity dams around central Queensland are also on standby to release water.
The "unusual" weather event is being driven by a surface trough which has developed in the Coral Sea and tracking southwest towards the Queensland coast.
A separate upper trough is also moving through western Queensland, bringing thunderstorms and rain.
The Bureau of Meteorology's National Operations Centre senior meteorologist, Scott Williams, said it was shaping up to be a huge weather event.
"It's unusual to get a band that extends right across the country outside the traditional wet season," he said.
"(Today is) becoming very active for rainfall on the Queensland coast, especially the area from Innisfail down to Gladstone with totals broadly 100-200mm developing in that area and even some isolated thunderstorms ... west of Mackay could reach 400mm."
The rain event is then expected to shift south-easterly tomorrow, bringing showers to the southeast coast. Brisbane and the Gold Coast could get rainfall of up to 50mm before an overcast and drizzly weekend.
"Rainfall amounts ranging broadly from 30 to 60mm are also possible along the coast and eastern ranges near the Queensland border," Mr Williams said.
"Depending on how this system develops and tracks, higher totals are possible locally in that region as well."
Update your news preferences and get the latest news delivered to your inbox.