The ACT Emergency Services Agency earlier issued an emergency warning that it was too late to leave in the suburbs of Beard and Oaks Estate, before downgrading it to a watch and act.
"The fire may pose a threat to all lives directly in its path," the ESA said.
"People in these suburbs are in danger and need to seek immediate shelter as the fire approaches."
The fire in Pialligo Redwood Forest is almost 90 hectares, with conditions on Wednesday making it difficult to control.
"Properties may be impacted by embers well ahead of the fire causing spot fires,” the ESA said.
The fire near Canberra airport is burning in an easterly direction towards the suburb of Beard on the ACT-NSW border.
Although fire grounds across the state have received rainfall in the past week, the NSW Rural Fire Service has warned forecast high temperatures and winds could see fire activity increase on Thursday.
Temperatures are expected to reach 40C in Nowra on the South Coast, 43C in Penrith in western Sydney, 41C in Cessnock in the Hunter region and 42C in Bulahdelah on the Mid North Coast.
NSW RFS spokesman Ben Shepherd said low humidity and very strong northwesterly winds have crews bracing a potentially dangerous day.
"There is a broad area of severe and very high fire danger and areas of extreme fire danger," Mr Shepherd told AAP on Wednesday.
"All fire grounds have received some rainfall and that has greatly reduced some fire activity but we might still see some fire grounds pick up and move tomorrow."
Severe and possible extreme fire danger ratings are expected in Illawarra-Shoalhaven, Southern Highlands, greater Hunter and northwest NSW.
Total fire bans were in place on Wednesday in the state's southwest, far west and northwest where the fire danger rating was listed as severe.
The Bureau of Meteorology on Wednesday issued a severe weather warning for damaging winds in parts of the Riverina, Snowy Mountains and far western NSW.
Winds averaging up to 65km/h with gusts of 90km/h are expected on Wednesday afternoon and into the evening.
The BOM warned Thursday's damaging winds may extend to the southern tablelands, the central tablelands, the Illawarra and south coast.
The warning comes after severe thunderstorms hit Sydney, Newcastle and Wollongong on Monday, leaving homes and businesses without power.
More than 60 fires continued to burn across the state as of Tuesday night with 16 yet to be contained. More than 1100 firefighters were in the field.
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