The threat posed by a grass fire burning near the town of Maitland on South Australia's Yorke Peninsula has reduced, but the Country Fire Service (CFS) is urging locals to remain watchful.

Key points: A fire near Maitland spread quickly and blackened more than 50 hectares

A fire near Maitland spread quickly and blackened more than 50 hectares It has now been contained but the CFS is urging locals to remain vigilant ahead of more wild weather

It has now been contained but the CFS is urging locals to remain vigilant ahead of more wild weather At the height of the danger, the fire was moving towards the town

The blaze near Spencer Highway and Balgowan Road — about four kilometres northeast of Maitland — has now been contained, but blackened more than 50 hectares of grass, cropland and scrub after breaking out this morning.

The CFS earlier issued an emergency warning to Maitland locals, telling them they were in danger and urging them to take shelter.

That warning has now been downgraded to a bushfire advice message, but the CFS said the danger had not yet passed.

"The threat from this fire has reduced, however people are reminded to take care in the area," the CFS said in a statement.

A CFS spokesperson said more than 100 firefighters were called in, as well as 33 firefighting appliances and five aircraft including waterbombers.

"Locals will notice a very strong and visible smoke column coming out of this," CFS assistant chief officer Brenton Eden told ABC Radio Adelaide.

"It's under the influence of a very strong northerly wind, so the fire that started north of Maitland will be burning in a southerly direction towards Maitland and beyond.

"Our estimates from the Bureau [of Meteorology] suggest that for the next three to four hours that northerly wind will continue."

A map of the warning area for the fire near Maitland. ( Supplied: CFS )

Before being contained, the fire moved quickly as it was fanned by strong winds. The CFS said there was reduced visibility on the roads and a risk of trees and branches falling.

A fire weather warning issued by the weather bureau remained in place for the West Coast, Eastern Eyre Peninsula, Lower Eyre Peninsula, Mid North, Mount Lofty Ranges and Yorke Peninsula forecast districts.

A low pressure trough was expected to bring more wild weather, including areas of raised dust and possible gusty storms, as it crossed the state.

"We're hoping around the entire state that people are very vigilant today," Mr Eden said.

"We are going to experience two seasons in 24 hours, 36 hours. We're going to go from very dry air at the moment — very hot dry air, very dangerous fire conditions — to within 24 hours we'll probably be reporting trees down and wind damage.

"The risk for us is that we get fires starting in other areas. We have the complication of lightning coming across the state today as well, before we reach those winter conditions."