Tasmanian police are investigating reports of a death in a huge bushfire in the state's south that has destroyed homes, and damaged a school and an RSL club.

Police say up to 65 buildings could have been damaged or destroyed in the small community of Dunalley, 55 kilometres southeast of Hobart.

Damaged buildings include the local school, the RSL club, a service station and houses, ABC television reported.

Around 15 houses at nearby Boomer Bay could also have been lost as the impact of catastrophic fire conditions in southern Tasmania begins to emerge.

Tasmania deputy police commissioner Scott Tilyard said a team was on the ground to investigate a fire crew's concerns that a man may have been trapped while trying to defend his house.

"We can't at this early stage rule out that there has been loss of life," Mr Tilyard told reporters in Hobart.

He said around 50 people were awaiting the arrival of police boats to help them leave the waterfront near the top of the Tasman Peninsula where they had taken refuge.

The Tasman Peninsula, including the popular Port Arthur tourist destination, was completely cut off by the closure of the major Arthur Highway.

Around 600 people were taking refuge at temporary accommodation at Nubeena and 1500 people were reported to have visited the Port Arthur convict ruins on Friday.

"Those people are being looked after as best we can," Mr Tilyard said.

"The main thing is they are safe."

People had also been told to leave the beachside town of Dodges Ferry.

Fire crews were monitoring potential spot fires further south at Eaglehawk Neck and banking on a southerly change due late on Friday night to stop the fire from spreading.

Huge plumes of smoke were visible from Hobart as the island capital sweltered through its hottest day on record. The temperature reached 41.8C at 4.05pm (AEDT), the hottest it has been since record keeping started in 1883.

Winds gusting to 100km/h whipped up the two largest blazes that had started on Thursday; at Forcett, near Dunalley, and Lake Repulse near Mt Field National Park northwest of Hobart.

Tasmania Fire Service (TFS) Chief Officer Mike Brown said conditions on Friday had reached the catastrophic level in the rating system that was developed after the Black Saturday fires in Victoria.

"We reached catastrophic fire danger ratings at times during this afternoon," Chief Officer Brown told reporters.

"I don't think we're quite out of the woods yet."

The threat posed by the second major fire, which authorities suspect was started by a campfire, had eased by Friday night.

A grass fire at Epping in the state's north had been contained, but reports had emerged of a property being lost near Bicheno on the east coast.

Mr Brown said the change would bring lower temperatures and higher humidity but little rain.

"Tonight we still consider that there's a serious danger," he said.

Acting premier Bryan Green said the state government would provide whatever emergency assistance was needed and would liaise with the federal government.

Authorities say smoke is likely to be visible for several hours and people sensitive to it should stay indoors.

- AAP