© Supplied: Donna BussDonna Buss's frosty yard in Cudlee Creek.
The mercury dropped to 0.9 degrees Celsius at Adelaide's central West Terrace weather station about 5:20am — the coldest temperature in the city since June 24, 1944.
The record low at the site is 0.6C on July 24, 1908, although even colder temperatures have been recorded at the former main weather station at Kent Town.
The temperature at Parafield Airport in Adelaide's northern suburbs dipped to minus 2.4C, its lowest minimum since local records began.
Adelaide Bureau of Meteorology (BOM) forecaster Jenny Horvat told ABC Radio Adelaide a high east of the city was keeping temperatures down.
"It's quite a dry air mass, which is making it easier to get to those low temperatures," she said.
South Australia's coldest overnight temperature was minus 4.6C at Gluepot, north of Waikerie.
Footage also emerged this morning of ice on the surface of Adelaide's River Torrens.
ABC listener Caralyn said she stopped along the upper Torrens with her children just before 9:00am when they noticed the icy layer on the river.
"I've never seen the river freeze like that before. It's amazing," she said."[The] kids were all late for school while we explored."
Subzero temperatures in the Riverland over the past few days have damaged citrus crops.
Sunlands grower Peter Walker said the mercury has dropped to as low as minus 4.5C for the past couple of nights.
He has been applying molasses to his trees, as well as watering the canopy, to prevent further frost damage.
"It's like a burn. It ruptures the sap in the young shoots and they look like they've been burnt," he said."They'll recover. It's not the end of the world just yet.
"I can remember in 1982 where we had minus 6C for over a week and that was devastating to the region. We're a fair way away from that."
Warmer overnight temperatures are expected in Adelaide on Thursday and Friday, the BOM said.
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