A wind change has turned a fire at Finniss, about 80 kilometres south-east of Adelaide, towards already burnt ground.
The blaze is still burning out of control in the general direction of Finniss, but with much less ferocity than predicted.
State CFS coordinator Mal Watts says people in the area still need to be following their bushfire survival plan.
"There's a lot of emergency service vehicles on scene and people can take their guidance from them," he said.
"There's over 170 fire fighters and 30 fire fighting appliances on scene, so there are a lot of resources on site."
Earlier today, a fire was contained at Cunningham west of Ardrossan on South Australia's Yorke Peninsula.
It took about an hour for firefighters and water bombing aircraft to stop the blaze from spreading.
Contained fires are still burning at Sevenhill in the Clare Valley, Burunga Gap in the Mid North and near McGillivray on Kangaroo Island.
Temperatures in the west of the state have begun to drop ahead of the change.
Earlier today, the temperature at Ceduna was 45 degrees Celsius while further along the coast at Nullarbor it was 25C.
Alison Cook from the Bureau of Meteorology says the change will arrive in Adelaide late this afternoon or early this evening.
"The south-westerly change that we're expecting has come through at Nullarbor so Nullarbor is in a southerly air flow with some cooler air coming off the ocean at the moment so that's why it's much cooler," she said.
Temperatures are expected to climb above 40C in most of the state's major towns.
Tops of 46C are forecast in parts of the state with Tarcoola in the state's north heading for 47C.
A top of 44C has been forecast for Adelaide after a low of 24.3C last night.
The last time Adelaide experienced conditions that hot was on January 28 2009 when the mercury climbed to 45.7C.
More than ten fires were reported yesterday with fuel loads extremely dry after months of low rainfall.
Conditions are forecast to be even hotter today and have led to fire weather warnings for all of the state.
The fire near MacGillivray on Kangaroo Island was brought under control yesterday afternoon after burning more than 80 hectares of crops, grass and scrub land.
The scrub fire near Sevenhill in the Clare Valley is continuing to burn inside control lines while a fire at Compton near Mount Gambier in the south east was contained yesterday afternoon.
Water bombing aircraft are on standby, with two planes arriving from New South Wales last night to bolster the fleet.
All national parks and reserves in the Lower South East will be closed because of the catastrophic rating in the region.
The National Motor Museum at Birdwood will stay shut today because of the same warning in the Mount Lofty Ranges
The 2009 heatwave pushed the state's electricity grid to breaking point and led to rolling blackouts.
Electricity distributor SA Power Networks also cut power to parts of the state's south coast at the start of last year without warning because of the risk of bushfires, a decision that angered some residents.
Company spokesman Paul Roberts says people should be prepared if the power is switched off today.
"We're monitoring weather across the state from weather stations across the state. The wind speeds are a particular concern," he said.
"The situation is that those localised conditions can change very rapidly.
"Any winds above about an average of about 42 kilometres an hour means you're likely to get trees and tree limbs falling on lines.
"That's when we're starting to get really concerned about the conditions and we're likely to be looking at disconnection."
Mr Roberts says the hot weather will drive up demand as people stay indoors.
"We're monitoring all our fuse operations across our transformers and there's 70,000 of them in South Australia," he said.
"There may be delays if there are other serious issues due to conditions including bushfire.
"If we have to turn off power in an area like the Mount Lofty Ranges then it's very likely the outage will be extended for a considerable time because we won't restore power until we've had the opportunity to check that lines are safe.
"We don't want to start a fire when we do the reenergising and that involves very significant patrolling in the Mount Lofty Ranges."
Power was switched off to more than 2000 homes and businesses in Adelaide's north-west this morning.
Supply was cut to Largs North, North Haven, Osborne and Taperoo before 7:30am.
The cause of the blackout is still being investigated.
Bureau of Meteorology senior climatologist Dr David Hones says the dry weather could continue throughout 2013.
"We've started the year with below average rainfall but a lot really does depend on what happens in the Pacific," he said.
"[It's] still too early to say whether we'll see an El Nino, a La Nina or neutral year."
Saturday is expected to provide a brief respite as temperatures drop into the low thirties but more hot weather is forecast to return early next week.
The air-conditioned Adelaide Central Bus Station on Franklin street will be open for 24 hours today to offer respite from the heat.
© ABC 2013
21:05 EST Authorities have sent emergency alerts to tens of thousands of people in NSW's Hunter region as forecasters warn wild weather will worsen after earlier claiming three lives.