A burst of spring thunderstorm activity has caused interruptions at Adelaide's Harvest Rock music event and the OzAsia Festival, amid more downpours in other parts of the state.

The Bureau of Meteorology said storms had moved across from the west, and that rainfall totals had exceeded 20 millimetres in some areas.

Power was also cut to thousands of properties, many of them in the Old Noarlunga area in Adelaide's south.

"We've got a lot of storm activity out in the west close to the WA border, pushing across the West Coast and Eyre Peninsula," senior meteorologist Miriam Bradbury said at about 4pm.

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