"I've been in this service for 25 years and I have never seen fire activity like this."
Rural Fire Service (RFS) Southern Highlands Inspector David Stimson warned residents not to be "complacent" as temperatures drop in the region.
The Green Wattle Creek fire has been burning across the Burragorang Valley area for nearly two weeks now.
The RFS lowered its status to Advice from Watch and Act on December 11.
But Inspector Stimson said that didn't mean local towns were out of danger.
"We'd like everyone around the fire zone to know that this fire is still not contained," he said.
"Although the fire has moved further south, all it would take is another really warm day and some westerly winds to change that - and those days have been forecast.
"We have established a large containment line from Buxton all the way to Wombeyan Caves by doing some tactical staged back-burning.
"We hope the tactical burning will turn the fire in on itself."
Residents were first warned to make preparations to leave and put their bushfire plan into action last month as the fire had jumped Lake Burragorang.
Locals in Oakdale, Warragamba, Silverdale, Werombi, The Oaks, Lakesland, Thirlmere, Buxton, Balmoral, Bargo, Hill Top and surrounding townships are still being urged to monitor conditions carefully.
The RFS staging area has moved from The Oaks to Hill Top as the fire moves south.
Mr Stimson said the drought was the main reason the fire remained uncontained.
"We have not seen conditions like this before," he said.
"The soil moisture content is so low that it is making it very difficult to put the fire out.
"We had fire at Oakdale the other morning that crowned (reached the treetops) at 3am - you never see fires do that at 3am."
Approximately 130 firefighters are on the ground helping to battle the blaze and build containment lines today.
A Werombi family has lost their home due to the fire.
A GoFundMe page was set up to raise funds for the Noble family by members of the Campbelltown Collegians Hockey Club.
More than $18,000 has been raised for the family so far.
Locals have also reached out to residents in the fire zones via social media pages to offer transport for livestock, use of their paddocks or a place to stay the night.
The Oaks Hotel, Narellan Community Centre and the George IV Inn have offered free shelter to residents who have been evacuated.
The council has also set up its mayoral relief fund for locals to donate money in support of residents affected by the fire season.