Pedestrians walk in heavy rain in the central business district of Sydney on February 22, 2022.

One person was found dead in a submerged car and 10 others were reportedly missing on Wednesday after heavy rain caused flash flooding in eastern Australia and set off a string of emergency warnings up and down the Pacific coast.

The body of the drowned 60-year-old was found early Wednesday in the state of Queensland, premier Annastacia Palaszczuk told parliament, describing the incident as a "tragedy".

Almost half a meter (1.5 feet) of rain has fallen on some parts of her state in the last 24 hours, causing multiple road closures and transport chaos.

Emergency services received more than a hundred calls for help and swift water rescue crews have been despatched to assist dozens of stranded residents.

Emergency services have received more than a hundred calls for help and swift water rescue crews have been despatched to rescue dozens of stranded residents.

"This has the potential to be a significant rainfall event for south-east Queensland," Palaszczuk said.

A freight train overturned near the town of Gympie, although the driver was said to have minor injuries.

Local media quoted Sunshine Coast Police District Superintendent Craig Hawkins as saying 10 people were also missing.

Fifteen Queensland dams are at capacity and more rain is expected in the coming days.

A woman takes pictures of the overflowing Parramatta river at the ferry wharf in Sydney.

"Locally intense rainfall is possible and since many catchments are now saturated there is an increased risk of dangerous and life-threatening flash flooding over the coming days," said Palaszczuk.

Police warned motorists to avoid driving through flooded roads and to stay at home.

"Flash flooding is occurring on roads and bridges - Re-consider your need to travel today," police told residents.

Heavy has also pelted the state of New South Wales, where parts of Sydney were briefly submerged Tuesday.

After several years of drought and climate-worsened bushfires, Australia's east is wrapping up an extraordinarily wet antipodean summer, thanks to a La Nina weather pattern.

La Nina increases the chances of tropical cyclones off Australia's Pacific coast and brings above-average rainfall, according to the country's Bureau of Meteorology.