Illawarra RFS district officer Col Church said there was a possibility the fire in Wollondilly could jump over the Hume Highway if it was not contained before Saturday.

"There will be another big effort on Saturday," he said. "Our volunteers will step up and continue their work."

"There is a likelihood that could occur," he said. "Crews are in a fight to contain the fire before Saturday."

"We need to face facts: it could come into the Illawarra area," he said

"We are liaising with the incident management team and planning our response. We will continue to work with them to instigate our pre-incident planning."

Mr Church said residents needed to consider their bushfire survival plan now and know what they would do if major roads close quickly.

"People also need to plan their travel when going on holidays," he said.

Mr Churcher explained two strike teams worked 12-hour shifts to help local crews fight the fires south-west of Sydney on Thursday.

The teams had about 22 and 26 firefighters, each with a strike team leader.

The second team was deployed around 2pm when properties were under threat in the Bargo area.

Mr Church said the control centre in Albion Park was a hive of activity on Thursday.

"There was a Fire and Rescue strike team on standby, as were a number of local stations," he said.

"We had our communications team working hard and the community engagement team provided advice to residents.

Mr Church said the fire control centre was manned until 11pm last night, with a normal crew today but would be ramped up with personnel again on Saturday for another day of hot and windy conditions.