Eastern Australia has endured torrential rainfall for more than a week, leaving hundreds of homes flooded, damaging roads and bridges and soaking farmland in Queensland, New South Wales and Victoria states.

"We have a damages bill at the moment that my guys are telling me is heading way north of $500 million," New South Wales Roads Minister Duncan Gay told ABC radio, adding that the state had been "horrendously hurt".

"The weather forecasters are telling me that April will be the worst that we've faced yet," due to a weather pattern known as "La Nina".

La Nina conditions typically bring higher-than-normal rainfall with Sydney on Thursday feeling the force of nature with an estimated 119 millimetres falling on the city – the highest daily total since 2007.

As the waters eased in some areas across NSW, communities downstream from the floods were bracing for the surging torrents yet to pour through the Murrumbidgee, Lachlan and Hawkesbury river systems.

In Sydney, where heavy rain Thursday swept away cars and flooded railway lines, residents on the city's north-western outskirts were being urged to prepare to evacuate their homes.

Further inland, residents of the country towns of Condobolin and Narrandera were bracing for the coming floods and people in the Victoria town of Nathalia were hoping their levee would hold.

Elsewhere, such as in New South Wales's biggest inland city of Wagga Wagga, emergency officials began the massive clean-up as flood waters began to subside. But residents were still faced with waterlogged homes and farms.

"It's fairly devastating but what else can we do? I don't think we are as bad as some people. I don't know what our losses would be," one flood-hit farmer, Lance Gillespie, told the ABC.

Hundreds of fire and emergency workers were hosing out homes, businesses and schools and clearing roads, Deputy State Emergency Operations Controller Assistant Commissioner Mark Murdoch said.

"While it's not over yet, some areas are starting the process of recovery and that generally begins with cleaning up," he said.

So far two people have died in the floods, after they attempted to cross waterways in cars.