Up to 300-500mm predicted to fall in some areas until Thursday – 10 times their average monthly rainfall.
Sky News Weather chief meteorologist Tom Saunders said the wild weather was sparked by cold air from the west pushing into warm air from the Coral Sea to the North.
‘The warm air gets lifted above the cold air because it’s not as dense and it’s that uplift that leads to clouds, which in this case will be widespread across Queensland and cause heavy rain,’ he said.
‘Tomorrow we will have widespread heavy rain through the central inland parts of Queensland, some heavy rain in the northwest and north coast, but also a risk of some heavy falls through the southern part of the state including the southeast.
‘So, much of Queensland will start to get heavy rain on Tuesday.’
Police warned locals to avoid unnecessary travel, including for holidays or work.
Most of the rain will be dumped along a 700km stretch of coastline from Townsville to Rockhampton and inland to Longreach and Winton.
The central, central interior, and central coast are all forecast to get 10 times their monthly average, and the interior and southeast to get an average month’s worth of rainfall.
The wet weather will spill over into NSW with rain forecast for parts of the state until Sunday.
Acting Inspector Donna Stewart said one in 10 road deaths in Queensland this year were from people driving in floodwaters.
‘It’s incredibly frustrating to see the number of people who aren’t heeding our warnings,’ she said on Sunday.
Bureau of Meteorology senior meteorologist Felim Hannify said the heavy rain that started on Monday would also bring damaging winds.
‘There’s going to be widespread rainfall basically across the entirety of the state,’ Mr Hannify said.
‘The real event starts to ramp up particularly from Tuesday to Wednesday.’
Showers are expected in Sydney every day until Sunday. The mercury will reach a maximum of 23C and a minimum of 15C.
Higgins Storm Chasing chief forecaster warned the massive downpour would be the biggest threat from Gladstone up to Port Douglas on the Queensland coast.
Whilst 300-500mm is a “normal” wet season weekly total for these areas – the biggest issue will be when likely convergence zones develop and cause 200-300mm in a matter of hours,’ he said.
‘This could result in locally much higher falls than what is being forecast. When and where these convergence zones occur will be primarily a ‘live’ thing to cover.
‘Some flooding is likely with these falls, with flash flooding being a big concern too… almost a daily concern from Tuesday onwards.’
Mr Hannify warned parts of the state were already saturated and flooding presented a threat to lives and livestock.
He said the severe weather would be fuelled by two troughs, one coming from the interior and another from the north coast.
A high pressure system in the Tasman Sea will essentially trap the two rain-laden troughs across Queensland, forcing it to rain itself out rather than move on.
‘It’s like nature is working against us,’ Mr Hannify said.
Premier Annastacia Palaszczuk urged residents to ‘lean forward’ in the coming rain event with saturated catchments unlikely to cope, increasing the risk of flash flooding.
‘We will be monitoring it very carefully,’ the premier said on Friday.
‘It’s very unusual to see this type of situation occurring in far north Queensland, especially this time of year which is usually near the end of the season.
‘We are expecting higher rainfall totals than we’ve seen before in May.’
Queensland and NSW are still reeling from devastating and deadly floods earlier this year which triggered a massive – but criticised – response from state and federal governments.