The entire South Australian coastline is under a severe weather warning with rain and damaging winds up to 100km/h on the way.

Perth and the South West are set to be pummelled by "tornado-strength" wind gusts and dangerous swells in "once in five-year" storm.

As the massive storm's set to bare down on parts of WA, the coastal town of Lancelin is tonight on high alert as huge swells threaten to breach its already eroded coastline.

Perth and large parts of the WA coastline are set to be smashed by severe rain and thunderstorms today.

The entire South Australian coastline is under a severe weather warning with rain and damaging winds up to 100km/h on the way.

Residents in South Australia are being warned to expect rain and damaging wind today.

South Australia is one of four states set to be smashed by severe weather this week.

Damaging and destructive winds are set to smash large parts of South Australia after wild weather swept the state.

Weather alerts have been issued for dangerous high tides and flood risks.