A flood advice message for people along the upper and middle Onkaparinga River has been issued by the State Emergency Service (SES) as rain continues to fall across South Australia.

Water across the road at Kangarilla. ( ABC News: Rebecca Opie )

The service issued its flood risk advice for properties and roads upstream of Mount Bold Reservoir in the Mount Lofty Ranges.

People have been told floodwater "may threaten you and your family's safety" and that they should follow their emergency flood plans.

The front is expected to dump between 80 millimetres to 120mm of rain in the elevated areas in the ranges during the next few days, while a gale warning has been issued for coastal areas.

SES state duty officer Ian Bonython said crews were on standby and believed their time would be spilt between the Adelaide Hills area and the coast.

Mr Bonython said on Tuesday crews had been called to remove trees from roads and as the rain set in, more jobs involving flooding through roofs had been received.

"The most important thing for the people who come across any flooded waters is to stay away," Mr Bonython said.

"Don't walk, don't drive through them. Find an alternate route and that's the safest possible thing you can do.

A Bureau of Meteorology satellite image of a cloud band covering SA's south at 4:00pm. ( Website: Bureau of Meteorology )

"We have had too many deaths in interstate through drowning, through going through flooded waters."

Mr Bonython said there had been one incident where a driver was rescued by passers-by after trying to drive through floodwater.

Emergency crews were called to a number of properties in Kangarilla, south of Adelaide, to provide sandbags in preparation for flooding.

Heavy downpours during the afternoon caused flooding in one home with some minor damage to the garage.

There was flooding on the main road through the town and in surrounding paddocks.

Floodwaters across Oakwood Road at Oakbank. ( ABC News: Rebecca Opie )

BOM warns of rain and damaging winds

Bureau of Meteorology (BOM) state manager John Nairn said there was a minor flood warning for the Onkaparinga River, a flood watch for the Mount Lofty Ranges, a road weather warning and gale warning for coastal waters.

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"It's a pretty vigorous front with a rain band that's giving us this rain initially," Mr Nairn said.

He said the rain would ease this evening but further falls were expected in coming days, which may prompt further flood warnings.

"At the moment we are seeing something rather unusual for Adelaide.

"There's a broad band of rain that's been giving us quite decent rainfall in the last nearly 24 hours and a sustained period like that we don't see that too often nowadays."

By the end of Thursday, he predicted rain totals in elevated areas could be between 80mm and 120mm.

The system will affect areas from Western Eyre Peninsula to the South East. ( Bureau of Meteorology )

As of 9.00am Tuesday, the weather bureau had already recorded rainfall totals of 25 to 30 mm over the Mount Lofty Ranges, causing water levels to rise in the upper Onkaparinga catchment.

It said the severe weather system would bring another 15 to 25mm over the Mount Lofty Ranges and it issued a flood watch for the district.

It warned that localised minor flooding would again be possible on Thursday, particularly in the upper Onkaparinga catchment and possibly the upper Torrens and that some roads might be closed.