Perth has endured its coldest morning in four years, with the temperature plummeting to 0.6 degrees Celsius in the early hours, as much of southern Western Australia braved freezing conditions.

The Bureau of Meteorology (BoM) recorded the low temperature at 7:09am.

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It marks Perth's coldest night since July 25, 2012, when the city recorded 0.4C.

The southern suburb of Jandakot was the chilliest spot in the metropolitan area, with the temperature plunging to -1.6C.

It was even colder in parts of WA's South West, with Bunbury recording its equal lowest mark in six years at -0.3C.

Elsewhere, Collie East dropped to -3.7C and Bridgetown -2.4C.

The town of Wandering in the Great Southern got down to -3.8C.

BoM duty forecaster Ricus Lombard said the cold conditions were being caused by a big dry ridge sitting over the southern half of WA, combined with light winds.

He said the cold air followed a front that passed over the area on Monday.

The overnight low is expected to remain in single figures until Friday, when a new weather system hits the state.

Morning conditions are expected to remain chilly in Perth until Friday. ( ABC News: Lauren Day )

Other states have been harder hit, with a cold snap across the south-east coast of Australia bringing freezing temperatures, wild conditions and snowfalls.

Two people were injure in separate car crashes in Victoria during a night of snow, hail and high winds.

Thousands of homes in South Australia and Tasmania remain without power after strong winds lashed the two states.

However the worst is yet to come in New South Wales, with snow beginning to fall in the Southern Tablelands and damaging winds expected.

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