Residents across parts of Adelaide have awoken to the smell of smoke, with a burn-off in the Adelaide Hills believed to be the cause.
There have been reports of smoke from the north-eastern suburbs including Windsor Gardens, as well as the inner south, Prospect, foothills and the CBD.
The Bureau of Meteorology (BOM) said the likely cause was a prescribed burn at Montacute, north-east of the city.
"The winds around the metro area ? they're generally light north-easterlies," forecaster Simon Timcke told ABC Radio Adelaide.
"Often at night, you get a low-level inversion and the smoke can get trapped underneath that and just stay fairly still through the night.
"There have been a few prescribed burns going in the hills. I think there was one up at Montacute yesterday, so I do wonder whether we've got a little bit of smoke drifting down in that light north-easterly.
"Once the sun gets up and a bit of wind gets going it'll hopefully mix that out. Without knowing 100 per cent what it is, that'd be my guess."
The Country Fire Service (CFS) website lists no uncontrolled bushfires, but does mention a controlled burn at Montacute.
CFS state commander Sam Quigley said the Department for Environment and Water had been carrying out five burns, three of which were likely fanning the smoke.
He said the smoke was "absolutely related to the prescribed burns", and it was unusual for it to linger so long.
"Prescribed burns aren't often that large," he said.
"Given that there were a couple in the general area of the Adelaide Hills, and with the north-easterly winds, the smoke's condensed or concentrated."
BOM forecaster Jenny Horvat said the smoke would gradually clear as the weather changed.
"We've had a bit of an inversion develop overnight, so it's been trapped," she said.
"With the light north-easterly winds, it's drifted back over the city but I think most of that should be starting to dissipate pretty quickly. We've got some showers coming across from the west."
Amid the showers, smoke haze and glow of the rising sun, there was a large double rainbow in the sky above Adelaide.
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