The Tasmanian Fire Service posted emergency warnings for two large fires in the island's south that broke containment lines.

The Bureau of Meteorology said Hobart had its all-time record of 41.3 degrees at 1.53 pm on Friday, exceeding a 1976 record of 40.8 degrees, with hot and gusty northerly winds pushing the fires.

East of Hobart, a fire that began on Thursday crossed the main Arthur Highway, forcing police to close all road access to the tourist destination of the Tasman Peninsula.

The TFS said embers ahead of the main front were falling on the community of Dunalley, and houses were also reported to be under threat in the town of Forcett.

The service's acting district officer, Andrew McGuinness, said the blaze had taken a significant run in severe conditions.

Mr McGuinnes said another of the worst fires was burning near Ellendale in the Derwent Valley, west of Hobart.

Mr McGuinness, said this blaze, which began on Thursday in bushland, was expected to reach the farms and small-holdings around Ellendale within hours.

Police said it appeared that this fire started on Thursday from a campfire that was not properly extinguished on Wednesday night, before a total fire ban was imposed

Several hundred firefighters using 114 units were fighting a total of 19 fires with no relief in sight from the conditions until later on Friday night.