I member reading that one of the largest fires (by area) ever recorded was in the outback relatively recently. It was only discovered weeks after the fact because they don't have satellites to monitor fires in the middle of nowhere.

But also, the outback is most of australia, and even the driest areas still have buffle grass scattered close enough for fires to easily spread between them.

The Outback is a remote, vast, sparsely populated area of Australia. The Outback is more remote than what Australians call “the bush”. While often envisaged as being arid, the Outback regions extend from the northern to southern Australian coastlines and encompass a number of climatic zones, including tropicaland monsoonal climates in northern areas, arid areas in the "red centre" and semi-arid and temperate climates in southerly regions.