Australian emergency services Monday ordered thousands more to evacuate a New South Wales town threatened by rising floodwaters, as the crisis claimed a second life when surging water swept a car off the road.

Days of heavy rain have hammered the eastern states of Queensland, New South Wales and Victoria, swelling rivers, flooding farmland and forcing the closure of bridges and roads.

New South Wales emergency officials and police ordered thousands to evacuate the centre of the town of Wagga Wagga late Monday as the Murrumbidgee river threatened to breach the city's levee barriers.

People had already been ordered to evacuate homes in the surrounding area after the river burst its banks in places.

"We're encouraging people to move now," State Emergency Service spokesman James McTavish told the AAP news agency.

"Don't delay. This is a very serious issue."

Across New South Wales, more than 5,000 people had already been ordered to evacuate, with another 2,000 stranded.

In Wagga Wagga, residents earlier said there was an eerie calm, as floodwaters surged under blue skies and sunshine.

"It's so strange, it's a beautiful day in Wagga, so we're just sitting around, drinking tea and waiting for the river to quietly engulf the floodplain," local man Tim Kurylowicz told AFP.

"What was a relatively small river two days ago is like an endlessly wide lake, with treetops swishing amongst the water," added Kurylowicz, who had already been evacuated on Monday to an unaffected part of the city.

Authorities again warned people against driving their cars through floodwaters after more than 30 rescues overnight, including that of two adults and three children who had been trapped in a car in Wagga Wagga.

One man died at Araluen in southern New South Wales at the weekend after being washed downstream as he attempted to drive through floodwaters. His two companions were rescued, one reportedly clinging to a tree.

And the toll rose Monday after a man died when his car was swept off a road in heavy flooding in the southeast Queensland town of Glenwood, near Gympie.

Police said they had been unable to confirm a report that a second vehicle was also swept away.