Prime Minister Julia Gillard has offered her condolences after three people died in Queensland, saying the floods had ''broken a lot of hearts''.
Ms Gillard, who was touring bushfire-affected parts of Victoria, said nature was challenging the nation but people would ''get through this'' by pulling together.
Brisbane floods 'heartbreaking'
Restaurant staff along the Brisbane riverfront prepare to be flooded for the second time in two years while residents in suburbs are "devastated' by rising water Monday.
Opposition Leader Tony Abbott dropped into an SES depot in Brisbane to fill sandbags as it braced for flooding.
Deputy Prime Minister Wayne Swan visited Goodna, in Ipswich, west of Brisbane, where residents have been put on flood alert.
Ms Gillard said Bundaberg, Rockhampton, Ipswich and Brisbane were among cities affected by the wild weather and evacuations were occurring in Grantham and Laidley, in the Lockyer Valley, which was hard hit by a fatal torrent of water in the January 2011 floods.
''Given everything that has happened in Queensland over the last two years this is a particularly heart-breaking time for people,'' Ms Gillard said. ''Whether it's bushfires, whether it's floods we are being challenged by nature, but we are a strong and smart nation and we will get through this like we always do, by pulling together.''
She said she had spoken to Queensland Premier Campbell Newman and offered help.
So far, the Australian Defence Force has provided Black Hawks to help flood-affected communities.
As the wild weather moved towards New South Wales, Ms Gillard called on residents to heed advice from authorities.
''To the people of Queensland, we will be there working with you, alongside you as we face the consequences of this wild weather,'' she said.
Ms Gillard said people should be prepared for the bushfire season not being over yet and the weather could be hottest next month.
Mr Abbott visited an SES Depot where Brisbane City Council staff and volunteers are filling sandbags for the 3600 residential homes that could be affected by floods in the next few days.
Later, at Emergency Management Queensland headquarters in Brisbane, Mr Abbott said he had been impressed by the emergency response and how the people of Brisbane had rallied to confront the flood threat.
On Twitter, Mr Swan said from Ipswich: ''Just visited some homes in Enid St Goodna where people are evacuating-great to see so many people turning up offering to help #qldspirit.''
Mr Swan said five more Queensland areas were declared eligible for disaster assistance overnight: the Fraser Coast, Sunshine Coast, Gympie, Moreton Bay and North Burnett. This took the number of Queensland council areas eligible to 34.
Ms Gillard visited the Heyfield Incident Control Centre with Victorian Premier Ted Baillieu and Deputy Premier Peter Ryan for a briefing with senior officials before touring fire-affected areas at McEvoy's Point in Seaton and morning tea with CFA and community volunteers.