A strong cold front will surge through South Australia into Victoria, New South Wales and Queensland from Monday, bringing a wave of below-average temperatures to the states.

A severe weather warning for gale-force winds has been issued for most of NSW, with conditions set to worsen into this evening.

NSW residents are warned to expect winds in excess of 90km/h, while thunderstorms are forecast for Sydney today.

Those in Melbourne will also vouch for the drop in temperature, as the city faces its coldest day so far this year, with a forecast top of 12C.

Brisbane will see the colder weather later in the week, with Thursday expected to be the weather system's peak.

And West Aussies are not immune to the cold either; over on the other side of the country, northern parts of Western Australia have been battered by rain as another cold front puts a chill through the state's south.

The unseasonal rain brought flash flooding to parts of the Pilbara coast, with cars trapped by floodwaters outside Whim Creek.

The heavy rain will move east over the coming days, with flood warnings in place across the Pilbara.