Australia’s most populous state of New South Wales (NSW) has issued more evacuation orders following the worst flooding in decades.

The NSW State Emergency Services responded to 640 calls for help on Saturday night, including 66 for flood rescues.

NSW Premier Gladys Berejiklian said that hundreds of people have been rescued from the waters.

Evacuation orders have been issued at multiple locations on the state’s mid north coast, which Ms Berejiklian said was experiencing a one-in-a-100-year event, and “whilst we don’t think things will worsen on the mid north coast, definitely conditions will continue, so the rainfall will continue across the parts that have already been affected”.

Ms Berejiklian also said that parts of Western Sydney are being hit by a one-in-50-year weather event, with some locations recording more than 11.8 inches (300 millimetres) of rain since Friday morning, breaking records.

The Warragamba dam, west of Sydney, started overflowing on Sunday and 13 evacuation centres have been opened across the state. More evacuations are expected as the bad weather is forecast to last into the middle of the week.

Local authorities are urging people not to drive through flooded areas as they could get easily swept away by the strong currents.