Two homes are believed to have been destroyed in a bushfire burning at Eden Valley north-east of Adelaide.
A thick plume of smoke is billowing over the wine region as the fire takes hold of Marne Park at Eden Valley near the Barossa.
The hilly terrain is making it difficult for fire fighters to get to the blaze, which is spreading in multiple directions, and the CFS says people in the area should follow their bushfire survival plans.
The blaze is one of 17 fires across the state, with other significant blazes at Bangor, Ngarkat and north of Renmark.
CFS Chief Officer Greg Nettleton says firefighters are also bracing for a series of new fires with lightning on its way.
"At this stage I can't give you prediction of where fires might start today," he said.
"It depends on where lightning lands but our briefing with the bureau indicates that we expect to see lightning strikes across the Eyre Peninsula earlier on this afternoon and they'll traverse across the state as the change moves through."
Emergency relief centres have been set up in Renmark and Port Pirie as fires burn in nearby areas.
Residents at Napperby near Port Pirie have been told wind changes expected later this afternoon could make a fire at Bangor in the Port Germein Gorge unpredictable.
About 150 residents and emergency service chiefs packed the local tennis club rooms for the public meeting on the fire situation.
Region coordinator Bluey Devine told the meeting the communities of Nelshaby and Napperby are not currently at risk, but wind changes in four to five hours' time could push the fire towards the two towns.
Metropolitan Fire Service crews are on standby in Port Pirie should nearby towns come under threat.
Fire burning near Renmark in the Riverland
The CFS says a fire on Calperum Station near Renmark in the Riverland could affect properties at Renmark West and Monash.
The blaze is heading in a southerly direction towards Cooltong.
Regional commander Richard Coombe says more crews are being sent to deal with it.
"We've actually also increased resources up there. We've got crews up from Adelaide who'll actually be up here for a couple of days," he said.
"We're getting an aerial flight as soon as we possibly can to plot the actual progress of the fire and where it is so that we can do predictions to actually allow us to provide community messages."
The could be the most dangerous day of the current heatwave because of the wind threat.
There have been more than 450 fires across South Australia since Tuesday as the state has swelters through a severe heatwave.
CFS state coordinator Brenton Eden says winds have driven the Bangor fire in all directions.
"We are responding a strike team of MFS appliances up to Port Pirie so that they can engage in asset protection up there," he said.
"Today is not looking like a good day for a fire fight. It will be a major effort."
Police are asking people to stay away from bushfire areas where possible after overnight spectators hampered the efforts of firefighters at Bangor.
"People curious more than anything driving around road blocks," he said.
"That caused a significant issue for emergency services, in particular CFS crews trying to fight the fire."
Fire escapes conservation park boundaries, residents evacuate
In the Upper South East, farmers have evacuated four homesteads because of a bushfire burning out of control around the Ngarkat Conservation Park in South Australia's South East, near the Victorian border.
CFS state coordinator Brenton Eden says the fire "raced out of the park at an incredible speed" towards properties.
Robyn Verrall lives on the edge of the park and says she spent the night defending her home.
"We actually had fire come through at about 8:00pm last night, so it's pretty big and we're still surrounded by smoke and lots of red sky," she said.
Wind change reaches West Coast
The Bureau of Meteorology's Brett Gage says the change has pushed across the West Coast and will reach Adelaide later today.
"The winds might turn westerly about western suburbs early afternoon giving a little bit of relief there but we're still expecting to briefly get to 42, 40 down in the coastal suburbs," he said.
There are hopes the threat posed by several fires on the state's west coast will ease as conditions cool down.
Fire north of Ceduna in the Yumbarra Conservation Park, near Kiana on lower Eyre Peninsula and in the Gawler Ranges continue to burn.
Local CFS coordinator Justin Woolford says the fires are still a concern but the wind change should help.
"There's been significant work done overnight with heavy machinery on several fires to strengthen control lines for this wind change and the firefighters are reasonably confident those lines will hold," he said.
A fire continues to burn in the Gawler Ranges while patrols continue on a fire at Ungarra that has been contained.
Health staff boosted for final day of heatwave
The temperature in Adelaide has now risen above 40 degrees Celsius for the fifth consecutive day after another stifling night.
SA Health says more than 160 people have needed treatment in city hospitals since Monday.
SA Ambulance Service has attended a high number of people collapsing and others with pre-existing conditions made worse by the heat.
The service's Brian Ward says extra staff have been put on.
"We've put on extra resourcing over the last few days and continuing through into the weekend, both to cater for the increased demand from the ambulance service but also to allow our staff some respite in the heat," he said.
An elderly woman died in a suspected drowning at the beach at Semaphore Park yesterday afternoon in the extreme heat.
Police say she was pulled from the water by onlookers, who left before emergency services arrived.
Tram services in the city have resumed after the heat stress on the track forced them to shut down this morning.
© ABC 2014