Heat records topple as SA swelters

A town in South Australia's west has recorded the state's hottest-ever December day, as the state swelters through a four-day heatwave.

Nullarbor broke the record when it hit 49.9C Thursday afternoon, while Ceduna, on the Eyre Peninsula, recorded its hottest day in more than 80 years at 48.8C.

Adelaide soared to 45.38C - its hottest December day since records began in 1997 - but that record could fall as soon as Friday, when the temperature is expected to reach 46C.

Other locations where December records were broken included Port Augusta on 48.5C, Wudinna on 48.4C, Roxby Downs on 47.3C and Minnipa on 47.2C.

Chrissy Stott, who volunteers at Flair on Eyre market store in Ceduna and lives about three kilometres from the town, said the shop closed earlier in the day because of the extreme conditions.

"No-one wants to be out in this weather," she said.

"The shops were quite busy early, everyone goes out in the morning but it's too hot later on."

Ms Stott said her main concern was the electricity connection in the town, and said she had made preparations in case power was cut for an extended period.

"A lot of people have bought generators just in case," she said.

"It's been out for a couple of days before, so you have to be ready for it."

The heat has forced the cancellation of events across the state, including Friday's Twilight Race at Morphettville and the Renmark Christmas Pageant.

Adelaide Metro was also forced to cancel afternoon tram services because of the conditions on Thursday.

"We recommend seeking alternative transport, including bus services," it said on Twitter.