Australia bushfires: 'Fire-generated thunderstorm' forms amid catastrophic conditions

A fire-generated thunderstorm formed above New South Wales on Saturday as "catastrophic" warnings remain in place across the state.

More than 100 bushfires continue to rage. A combination of temperatures above 40C, low humidity, and strong winds are adding to the struggle for the almost 10,000 emergency personnel mobilised to deal with the blazes.

The NSW city of Shoalhaven was met with apocalyptic scenes on Saturday. A photo posted to Twitter by the Rural Fire Service (RFS) showed the sky blanketed in dark smoke as the thunderstorm formed.

Residents were asked to monitor conditions and take appropriate action. NSW fire commissioner Shane Fitzsimmons said it's as bad as it gets.

"These are the very worst of conditions and given that we've got a landscape with so much fire active and burning in it, you've got a recipe for very serious concern."

Emergency warnings remain in place across the state. James Morris from the NSW fire service said fewer than half of the fires currently burning are contained.

"Unfortunately we're not going to see containment on these fires until we get significant rain, which is not predicted at this stage until the end of February."

More than 800 homes have been destroyed in the fires, and holiday travellers are urged to delay their journeys.