A Sunshine Coast man has died trying to cross a flooded road at Kilcoy, north of Brisbane, as heavy rain continues across south-east Queensland.

Emergency services were called to Mary Smokes Creek Road just before 4pm AEST after a person witnessed a vehicle sinking in flood waters.

A short time later, police retrieved the body of a man in his 70s.

Further north at Pomona, in the Sunshine Coast hinterland, authorities are searching for a woman who is missing after abandoning her car near a flooded causeway.

It is understood police, SES and firefighters are searching for the woman in bushland.

South-east Queensland is on flood alert as the weather bureau predicts up to 200 millimetres of rain will fall in the next 24 hours.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 4 minutes 30 seconds 4 m 30 s Severe weather warning for Qld's south-east Download 2.1 MB

The bureau's senior forecaster Michelle Berry says heavy falls have already drenched the region.

"We've actually seen around 80 millimetres recorded in Toowoomba now since 9am (AEST), so that's particularly heavy rainfalls occurring through there," she said.

"Also similar totals around that Sunshine Coast hinterland and Esk area."

While the rain is nowhere near as heavy as that recorded during the Australia Day long weekend when ex-cyclone Oswald caused widespread flooding, authorities are still warning that flash flooding is possible from Bundaberg south to Brisbane.

Late on Monday evening, the Lockyer Valley Regional Council said flooding was expected in the Laidley Creek area by early morning and urged residents in low-lying areas to evacuate or go to Laidley State High School.

At Gympie, residents are being urged to prepare for flooding, with the Mary River expected to peak at 16 metres on Tuesday morning.

Gympie Mayor Ron Dyne says the Kidd Bridge has been cut and the Normanby Bridge is expected to be inundated overnight.

Police say the Bruce Highway will likely be closed at the Kybong-Traveston area south of Gympie.

Councillor Dyne says homes are unlikely to be affected but some businesses in Gympie's CBD will be flooded for the second time this year.

"We are expecting a high of 13 metres at 11pm to 12pm tonight and about 16 metres by 9am tomorrow morning," he said.

"Now, 16 metres indicates that some businesses in the CBD will be impacted by water because they'll go in at 15.1 metres."

In Pomona, residents in low-lying areas are angry that nothing has been done to stop their homes flooding.

The town was hit by flash flooding this afternoon with water flowing through the yards of homes in Rifle Street, as well as inundating the fire station and cutting roads.

Mary Lehane's home has flooded about five times in the past 12 months and she is yet to move back in after being inundated last February.

"It's just stressed our family out. All we do is fight, because we're depressed," she said.

"People say, you keep going, you have to keep going. It's like when someone dies you've got to keep going, you got to get on with your life.

"But this, I've had enough - 26 years of it. I was told this was a drainage problem, not a flooded area."

Brisbane City Council is keeping watch and providing sandbags to residents, but it is hoping the slow-moving rain depression means less chance of flooding.

A motorist had to be rescued from the corner of James and Kitchener streets in Toowoomba. ( ABC: Arlie Felton-Taylor )

'Drain down mode'

Water management authority Seqwater is coordinating low-level releases from Wivenhoe and North Pine dams as a precaution.

Seqwater spokesman Mike Foster said the releases are likely to continue well into tomorrow.

"We're still very much in what we like to call 'drain down mode', which is just bringing those levels back to that temporary full supply or, in the case of Wivenhoe, maintaining it at that temporary full supply," he said.

"Whether we need to escalate those releases in both dams will very much depend on what sort of rainfall eventuates overnight.

"But again, the sort of size of releases that we're doing in comparison to the Australia Day weekend are certainly well under the sort of releases we're doing over that period.

"But we'll wait and see what mother nature brings tonight."

Bruce Grady from Emergency Management Queensland (EMQ) says residents across the south-east should be prepared for any flooding.

"We are starting to see some localised flooding, so again our message to people in vehicles, if it's flooded, forget it," he said.

The heavy rainfall caught out a school bus this morning when it became stranded in flash floods at Acacia Ridge on Brisbane's south side.

A group of 16 school children had to be ferried to safety by a swift water rescue team.

Sorry, this video has expired Thousands still isolated by NSW floods ( Lucy Carter )

Thousands still isolated

In New South Wales, emergency services on the mid and far-north coasts are focusing on re-supplying communities isolated by floodwaters.

Water levels are dropping and people are returning to their homes, but more than 19,000 people remain isolated.

SES spokeswoman Michelle Mavroyeni says it is a big job to provide them with essentials.

"What we are now doing is making sure the communities around those areas who still have an evacuation order over them, or previously had but it's now been lifted, are being looked after," she said.

Evacuation orders are still current for parts of Kempsey, Port Macquarie and Hastings.

A major inconvenience is the Pacific Highway which is cut into sections, making travel between Sydney and the state's north difficult.

The roads authority says it is not able to say when the highway will be opened between Kempsey and Clybucca or Grafton and Iluka.

Rusty intensifying

Meanwhile, Tropical Cyclone Rusty is continuing to intensify as it tracks towards the stretch of coast in Western Australia known as cyclone alley.

This afternoon the category two system was 295 kilometres north of Port Hedland and 345 kilometres west of Broome and nearly stationary.

The weather bureau says Rusty is likely to remain a slow-moving system, making it difficult to predict when and where it will cross the coast.

The bureau says further intensification is likely as the cyclone approaches the coast, adding there is a high risk that Rusty will cross the coast as a severe tropical cyclone.

A cyclone warning is current for coastal areas from Cape Leveque to Mardie, while a cyclone watch is current for coastal areas for adjacent inland areas of the Pilbara including Marble Bar, Nullagine and Millstream.