South Australia's emergency control centre has been activated ahead of severe thunderstorms set to dump 100mm of rain over the state in coming days.
A low-pressure trough is expected to bring thunderstorms across the state on Friday, after heavy rain began falling on Thursday, and residents are being warned to prepare for flooding.
Bureau of Meteorology senior forecaster Matt Collopy says some parts of SA could be hit with record rainfall for this time of year.
"That 50mm to 70mm of rainfall in some cases can represent two months worth of summer rain," he said.
The SES has staff rostered 24 hours through to Monday with all units across the state on active stand-by.
Duty Officer Sara Pulford said the SES expected to be busy.
"Up until 7pm tonight, the SES received 39 calls for assistance from the South Australian public," Ms Pulford said on Thursday night.
"We expect this number to increase rapidly as the front moves through the Adelaide metropolitan area and the Mount Lofty Ranges later tonight."
Ms Pulford said the SES had already been called to fallen trees and dropped branches and warned people to remain vigilant around large trees.
Sandbags were distributed to four locations in the Adelaide metropolitan area and Mount Lofty Ranges and Port Pirie Council also has sandbags available from two locations in Port Pirie and Crystal Brook.
The bureau warns winds gusts of up to 90 km/h are expected and a flood watch has been issued for the Torrens, Onkaparinga and Gawler rivers.
