The Bureau of Meteorology has extended the severe weather warning for Queensland's northeast coast, with the monsoon trough causing the destruction expected to track slowly south.

The flood risk now extends from Ingham, north of Townsville, as far south as Mackay.

Premier Annastacia Palaszczuk has again ordered schools that were closed in north Queensland on Friday to remain closed on Monday.

"We are in unprecedented times. There is more rain to come," she told reporters on Sunday.

Water levels have stabilised in Townsville, but that could change with very heavy falls expected to continue until the middle of the week.

Thousands of residents there have already fled their homes, and they've been warned it could take days for water that's swamped roads, yards, homes and businesses to recede.

Bruce Gunn from Bureau of Meteorology said the monsoon trough could generate tornadoes, with current severe weather warnings saying gusts of up to 125km/h are possible.

"There is some chance of tornadoes forming," Mr Gunn told reporters on Sunday.

"We've used the cyclone siren a few times already in this event. We have applied that in short bursts when there are events of heavy rain ...We will continue to do that for the most intense of hazards as they occur."

He said there'd been some reprieve for Townsville's Ross River Dam, with the heaviest of overnight falls north of its catchment.

Authorities have said the integrity of the dam is not in question.

It's currently sitting at 223 per cent of capacity.

Meanwhile, thousands of homes remain under threat after half-a-metre of rain fell on communities north of Townsville over Saturday night.

The state's flood emergency is spreading and is now starting to cause significant problems in some inland areas.

Thousands of properties remain at risk of flooding in Townsville and surrounding areas.

On Sunday, fresh flash flooding warnings were issued for Nome, Julago and Alligator Creek, south of Townsville.

There are concerns too for residents of Ingham and Halifax, north of the city, after a night of extraordinary rainfall.

Ingham recorded 500 millimetres in 12 hours, with nearby Halifax copping 415mm.

About 400 kilometres to the west of Townsville, the outback town of Hughenden is also under a flood warning.

The catastrophic monsoon trough, which is now also generating damaging winds, is expected to swamp and close the Ernest Henry Bridge, compromising access to the town.

So far Queensland Fire and Emergency Services crews have helped in 220 relocations from homes that had or were at risk of flooding.

The State Emergency Service has had almost 600 calls for help in the past 24 hours alone.

The Insurance Council of Australia has declared a catastrophe, with early losses put at $16.7 million and sure to rise dramatically.

Disaster assistance has been extended for communities in Townsville, Charters Towers, Palm Island, Richmond and Burdekin, the Queensland government has announced.

It will be delivered through the jointly funded Commonwealth-Queensland Disaster Recovery Funding Arrangements.

On Saturday night, residents in north Queensland spent a sleepless night hoping their homes remain safe from flooding during the one-in-100-year downpour.

About 500 homes were at risk of going under in Townsville with tens of thousands more properties at risk if the flood crisis worsens, as expected.

Police, soldiers and emergency services spent Saturday door-knocking in Townsville to warn residents who have been advised to watch out for updates on the disaster.

"If the rain continues overnight and into tomorrow, if we keep going the way we are today, we are talking about 10,000 to 20,000 homes," Chief Superintendent Steve Munro told reporters.

About 100 homes were evacuated near the bulging Ross River dam as water was released, but it was back up to 216 per cent capacity by Saturday evening.

Paul Shafer and his family lost two cars, a truck and a caravan when water was released from the dam, a risky move designed to spare the town from more widespread flooding.

He understood the decision but said it was demoralising to see the destruction at his Hermit Park park home.

"We have decided to stay rather than evacuate; we still have electricity but it will be a sleepless night ahead, that's for sure."

The rain and flash flooding began a week ago, causing power and phone outages, closing roads and businesses, and inundating homes.

Four tourists trapped in a car were rescued by a grazier in a helicopter after being stranded by the flooded Diamantina River near Middleton on Saturday.

State Disaster Coordinator Bob Gee is urging people to stay out of the water and check emergency and weather warnings - which are updated regularly.

AAP