Flood-ravaged Queenslanders can take comfort in the thousands of volunteers willing to roll up their sleeves and help in what will be a marathon clean-up.

Across the state 86 communities have been affected by flooding, including the state's capital, with some towns deluged three times by floodwaters.

The death toll in the south-east stands at 16, with the number of those missing revised down to 20. Grave fears, however, are held for 12 people still missing.

The search and recovery effort in the Lockyer Valley west of of Brisbane will continue today, with police warning the death toll could double.

Volunteering Queensland says it has 20,000 people registered on its books, including those from interstate, wanting to help.

A massive clean-up operation has started in earnest in Brisbane and Ipswich today as floodwaters continue to recede.

People are being asked to gather at four assembly points across Brisbane before they are bussed to suburbs needing help.

The assembly points are at the Doomben race course, the Boondall Entertainment Centre, the Mount Coot-tha Botanical Gardens car park and McGregor High School.

Lord Mayor Campbell Newman said two four-hour shifts were scheduled for 7:00am (AEST) and noon.

"If you know someone who owns a business, if there's a friend or relative you can help go and help them," he said.

"If you don't know a person or you don't know where to go, we'd like you to be part of our coordinated system for volunteers.

"How do you decide [where to go]? Well, let's try this simple little mechanism - get a 20-cent coin out, toss the coin. If you get heads we'd like to see you in the morning, tails in the afternoon.

"We ask people to come along to be self-sufficient - wear boots, long trousers, a long-sleeve shirt, hat, sunscreen, mozzie repellent.

"Bring water and food and be ready for your four-hour shift."

Mr Newman says volunteers may be needed for weeks, if not months, to clean-up the city.

More than 10,000 volunteers have already offered their help across Brisbane.

"My message to the community is this is a marathon, not a race. It will take time to clean up so please pace yourselves and be careful," Mr Newman said.

"For those who can't help this weekend, don't worry as there will be many more days when your help will be much appreciated."

Spirit and energy

To the west, clean-up efforts are also underway in Ipswich.

Mayor Paul Pisasale says it has been a long four days.

"Before the waters went down, there was a lot of spirit and energy," he said.

"As soon as the waters went down we looked at the devastation, we looked at people's dreams all in shatters.

"It has hit us by shock, but I can tell you we're coming back and we're coming back in a big way and we're going to do it with the support of the people who are coming in."

Water has affected more than 26,000 Brisbane homes, with 11,900 completely submerged and another 14,700 partially flooded.

The weather bureau says the state's sodden south-east can expect reasonably fine weather over the weekend.

Senior forecaster Peter Otto says the region will experience some cloud cover but no return of the heavy rain that has caused widespread flooding over the past week.

Power still cut

Nearly 27,000 properties across the south-east are still without power.

About 19,000 of those are in the greater Brisbane area, while almost 5,000 homes and businesses in Ipswich are blacked out.

Electricity has been restored to about 18,000 homes since yesterday afternoon.

Energex spokeswoman Kath Ryan says crews are working around the clock to get everyone back on line.

"For us it's a matter of waiting for the floodwaters to go down still," she said.

"We obviously can't get into areas where there's still inundation.

"So we just have to be patient with the rest of people and we'll get in there and get the power up and running when it's safe to do so."