Tasmanian firefighters are preparing for two days of very high fire risk, as specialist crews arrive to fight an uncontrolled bushfire in the state's World Heritage southwest.
The Gell River blaze, sparked by lightning strikes, has burned for nearly two weeks and through more than 20,000 hectares of wilderness.
Twelve firefighters from NSW will join efforts at the fire line on Friday, with temperatures forecast to pass 30 degrees in some areas.
"We are expecting (on Friday) low relative humidity and high temperatures about parts of the southeast and Upper Derwent Valley, which will generate very high fire dangers," Tasmania Fire Service chief officer Chris Arnol said.
"Fire in these conditions will start quickly and be hard to control."
The very high fire risk is expected to extend to the state's northwest and central north on Saturday.
Two helicopters from interstate are on standby in Launceston and Hobart, while the specialist teams will camp near the fire for several days with their own equipment.
Authorities have said the Gell River fire could burn for weeks if there is no significant rain.
A few millimetres of rain is forecast to fall on the fire in the next few days but not enough to have a significant impact.
A sprinkler line at Lake Rhona has so far protected sensitive plants from being burned.
A total fire ban is in place for Tasmania's southeast and central regions on Friday, while walking tracks in alpine areas of Mount Field have been closed.
The TFS has urged aircraft to stay away from the fire zone after an unidentified helicopter forced firefighting aircraft to be briefly grounded on Tuesday.