Adelaide has woken to its coldest start to an August day in 126 years and it was colder across other parts of South Australia.

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At 6:30am (ACST) the temperature was down to 0.9 degrees Celsius.

The weather bureau said it was the coldest August morning since 1888.

It was also the coldest day Adelaide has experienced in any month in six years.

Senior forecaster Mark Anolak said the low temperature has been brought on by cold air from the Antarctic moving over Adelaide.

"Under a ridge of high pressure that we are experiencing at the moment, clear skies have led to very cold temperatures over the last couple of days," he said.

"Murray Bridge has had its coldest ever start to the day in August at -2.7 degrees this morning."

Most of regional South Australia woke to cold and frosty conditions.

The weather bureau said it got down to -5.6C in Renmark, just above freezing in Lameroo and -3.9C in Loxton.

Clear, sunny skies lifted the temperature as the morning went on.