New Year's Day could be one of the hottest experienced in parts of outback South Australia, with temperatures expected to come close to the highest official maximum recorded across the nation.

That benchmark was set at Oodnadatta on January 2, 1960, when the mercury climbed to a scorching 50.7 degrees Celsius.

Temperatures there tomorrow are forecast to reach 49 degrees, with the same expected in Moomba the following day.

Bureau of Meteorology senior forecaster Domenic Pannucio says it is likely to be even hotter at some sites which are not monitored.

"It's definitely possible that there'll be areas exceeding 50 degrees across the north of the state," he said.

"Obviously we can only go by the locations where there are weather stations and there are a lot of regions there in the outback that we don't do readings for, so there certainly is some potential to get above 50 degrees in some parts of the outback."

But he says southern areas will be spared extreme heat.

"With the tropical cyclone that's coming into Western Australia weakening into a low pressure system as it moves down towards the south-western border of our state by Thursday morning, that's going to keep the heat from sort of pushing down into the south."

An extreme heat wave across much of Australia in January this year forced the Bureau to add more colours to some of its forecast charts for temperatures up to 54 degrees Celsius.

Total fire bans have been declared in eight of the 15 districts across South Australia today, ahead of the hot and dry conditions.