A fire-generated thunderstorm has formed over the South Coast on Saturday afternoon.
The Nowra fire control centre is watching closely as weather conditions converge and culminate in a dry thunderstorm causing erratic winds and dangerous fire activity.
Shoalhaven Rural Fire Service district manager Superintendent Mark Williams said the Currowan fire activity was creating a smoke column of up to six kilometres high and would start forming its own cloud formation above.
He said the fire ground where this was occurring was not threatening property or infrastructure.
"If the cloud keeps forming, it can create a pyro-cumulonimbus incident which can create its own thunderstorm activity including dry lightning," he said.
"If that happens, it ends up collapsing back to the ground.
"Erratic wind conditions on the ground in all directions can be created.
"The weather event can blow the fire in all directions over great distances in a short period of time.
"That is a significant concern to us.
"It is one of the most dangerous situations for a wildfire fighter to encounter."
Supt Williams said Shoalhaven RFS would be watching closely to see if the pyro-cumulonimbus would form.
"We responding to any movement of the fire as we need to," he said.
"The RFS head office in Sydney has the technology to watch it remotely through satellite imagery too.
"The thunderstorm wouldn't form in a small fire but as this one is very large, with a lot of landscape is on fire, a smoke column has been generated.
"Because the fire is burning such a large amount of land in an inaccessible area, there is absolutely nothing we can do about it."
Supt Williams said the thunderstorm could create dangerous conditions on the ground for firefighters.
"As soon as we get a warning of lightning storms then we will do an emergency broadcast over all of our radio systems," he said.
"We will make sure the troops in the field are aware of it and in safe locations clear of the fire ground.
If the thunderstorm is created, it would be the second time this week.
A pyro-cumulonimbus was created over Bateman's Bay on New Year's Eve.