More than 20,000 properties across Adelaide and the Adelaide Hills remain without power, as wild weather conditions begin to ease.

SA Power Networks says it is dealing with 137 separate outages with crews responding to widespread reports of storm damage.

The Bureau of Meteorology says sustained gale forced winds lashed South Australia.

Senior forecaster Brett Gage said such conditions, caused by an intense low pressure system, were rare.

"I'd say we get a system like this about once every two years," he said.

Gage said the highest gusts recorded were 132km/h at Neptune Island, 115km/h at Cape Willoughby, with numerous gusts of about 100km/h reported throughout the metropolitan area.

The coastal suburbs of Adelaide recorded between 10-20mm of rain, while the hills received up to 50mm.

Gage said the weather was clearing, but three more low pressure systems were expected to move through later in the week.

The State Emergency Service says it has responded to more than 1200 jobs since the "relentless" storm hit.

"People have woken up to significant damage this morning," Derren Halleday said.

"At Glenelg, we've had some rooves come off entirely, with people displaced."

Halleday said more than 500 volunteers were working to clear roads and repair damage.