The Tasmania Fire Service will take advantage of cooler conditions Sunday and undertake significant containment operations at Fingal, state public information officer Peter Middleton said.
Weather conditions "abated significantly" overnight, bringing cooler temperatures and higher humidity.
Hot, dry weather is expected to resume in the second half of the week.
"We've still got significant uncontained edges on this fire and we're just trying to get a picture on that this morning," Mr Middleton said.
"We're intending to hit these fires as hard as we can with aircraft and ridgetop lighting."
Ridgetop lighting consists of setting backburning fires at the top of a mountain and letting it burn down to create a buffer against the uncontrolled fire when it approaches.
This will create smoke, and Mr Middleton said the public should not be overly concerned.
"But if you are concerned, or if you suspect there may be new fires, call the TFS," he said.
The Fingal fire - which is made up two main fire blocks caused by embers from the first fire - is the only blaze burning at Watch and Act level on Sunday.
The original fire was allegedly deliberately lit, and a man was charged on Saturday with the crime.
The two fires have burned about 15,000 hectares.
Mr Middleton said there were still concerns the fire could spread into Douglas-Apsley National Park and from there, further along the East Coast.
"There's a long road ahead with this fire," he said.
Evacuated residents are returning to the town of Mangana, but Mr Middleton said there were still dangerous, burned-out trees which could fall in the area.
He urged returning residents to be cautious.