The Emergency Services of New South Wales state in southeast Australia warned on Wednesday there was now a risk of some flash flooding in the city of Newcastle.

The warning came amid news that the peak flood level of the Manning River further north in New South Wales will be at 4.3 meters instead of 3.7 meters predicted earlier as rain continues.

A spokeswoman from the State Emergency Service said the Manning River was expected to peak at around 3 a.m. Thursday morning local time and will impact an additional 40 properties.

Evacuations were underway for much of the day across the flood- affected regions in the state's north after one man died and three others were taken to hospital as rivers rose in the torrential rain.

More than 1,300 residents of the mid-north coast and Hunter regions have been affected by flooding after three days of heavy rain that has closed schools and roads and caused millions of dollars damage.