Residents in parts of South Australia's outback have woken up to a thick blanket of fog.
William Creek tourism operator Trevor Wright told the ABC he had only seen such thick fog on only a handful of occasions in his many decades of living in the outback.
"It goes for hundreds of kilometres ... [there's] thick fog at Maree, up towards Oodnadatta, over Lake Eyre," he said.
"Because it's such a dry, desert environment out here, it's extremely unusual to have fogs for a start, [especially] one of this density or thickness."
The Bureau of Meteorology said the fog was caused by an unusual amount of moisture in northern SA.
"We had a low-pressure system and trough move through inland parts of South Australia yesterday and overnight," duty forecaster Hannah Marsh said.
That saw thunderstorms drench some parts of the outback, with falls of 40 millimetres in Blinman and 21mm at Hawker.
"Then we had light winds overnight and with all this moisture around we ended up seeing very widespread areas of fog about inland parts, particularly the north-east and southern parts of the north-west and also the Flinders district as well," Ms Marsh said.
"Just being the start of winter it's quite common to see fog, but not as thick and as widespread as we've seen with this system."
The fog coincided with road closures throughout SA's upper north, due to the rain.
The Oodnadatta Track between Maree and William Creek is closed, as are roads between Yunta and the northern Flinders Ranges.
Mr Wright also said water from ex-tropical cyclones which came over Central Australia was now reaching Lake Eyre, filling the lake later than in normal years.
"It's unusual, because where it is in the Georgina system, not the Diamantina system, it takes longer for it to come down," Mr Wright said.
"What's interesting is that it goes through the Simpson Desert, right through it on the border of NT/Queensland and then down through South Australia.
"So, that system doesn't seem to get the amount of water I've seen in the last few years of what the Diamantina system gets."
More rain is forecast for the area later this week, meaning more potential road closures as people head north for the Finke Desert Race in Alice Springs.
