Wingecarribee and Wollondilly Rural Fire Service volunteers are bracing for worsening weather conditions this week.
The Green Wattle Creek fire has burnt more than 100,000 hectares since the incident started on Tuesday, November 26.
The current size of the fire is equivalent to 160 Wingecarribee Dams and 117 Cataract Dams.
The RFS planning section is implementing a long-term containment strategy, which involves the use of heavy machinery including bulldozers and graders.
The strategy identifies existing fire trails and tracks that require clearing and opening up, and new trails that need to be established.
Residents in the Northern Villages are advised to be aware of increased presence of heavy machinery and fire appliances on the roads.
Wollondilly Fire Control Centre community liaison Elizabeth Ellis said firefighters were "bracing for this week".
"It's been a good day for extending our containment lines because the wind direction is coming from the northeast," she said.
"The work has been undertaken with favorable conditions and has given us the opportunity to put containment lines on the western aspect of the fire.
"It's ahead of very high temperatures and worsening conditions for the week as a whole."
Residents living in surrounding areas are asked to monitor conditions and check the Fires Near Me website, the Bureau of Meteorology website and ABC radio.
"Listen carefully and don't panic. Listen to exactly what's being said in the area," Ms Ellis said.
"If you have not already, start a bush fire survival plan."
Wollondilly MP Nathaniel Smith has visited several RFS stations in the electorate to stay up-to-date with the current situation.
"I will be working closely with the RFS, SES, Fire and Rescue NSW and local councils to see what lessons can be learned from the current situation" Mr Smith said.
"I will also be consulting with those organisations and local residents to see what additional resources and protective measures are needed for the future."
The Southern Highlands will reach a top of 37 degrees on Tuesday, followed by temperatures in the late 20s on Wednesday and Thursday.
Cooler weather is forecast for the end of the week, with a top of 19 degrees on Friday and 22 degrees on Saturday.