The Tasmanian Fire Service (TFS) has said 20 or more homes are under threat from an emergency-level bushfire at Pelham in the state's south, and homes are feared lost in Tasmania's north-east in a separate emergency-level blaze.

Key points: Some areas are expected to reach over 40 degrees Celsius with high winds

Some areas are expected to reach over 40 degrees Celsius with high winds The TFS is warning any fires that start could travel quickly and spot eight kilometres ahead

The TFS is warning any fires that start could travel quickly and spot eight kilometres ahead Tasmania's Falls festival is going ahead, but contingencies are in place

The blaze at Horner's Road at Pelham, north-west of Bagdad, was upgraded to emergency just after 4:00pm on Monday, with the Elderslie warning upgraded soon after.

The Elderslie warning is about dangerous spot fires ahead of the main Pelham blaze.

An evacuation centre has been set up at the Brighton Civic Centre for residents leaving the fire zone.

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A second blaze on Mangana Road and Tower Hill near Fingal in Tasmania's north-east was also upgraded to emergency at 5:45pm, with an evacuation centre set up at 20 Talbot Street, Fingal.

Fingal itself was upgraded to an emergency warning just after 6:15pm.

Resident of Fingal, Gary told ABC Radio Hobart homes had been lost in that area.

"House have gone around Mangana and Tower Hill and we've had some spot fires in Fingal as well."

The TFS's Peter Middleton told ABC Radio Hobart the Pelham fire was very dry, making it hard to fight the blaze.

"The fire is fast-moving and going in a southerly direction," he said.

"People that are still in the area should travel to nearby safer places which are, if you're north of the fire to travel to Hamilton, or if you're south of the fire go to Brighton."

It's unclear if any property has already been lost, but Mr Middleton said the fire weather conditions were severe, and crews had had to pull back from the fire front.

Bushfires smoke is billowing over Strathgordon in Tasmania's south-west. ( Supplied: Paul Fleming )

"We've got flame heights that are 20 to 30 metres in height and it's very dangerous under these extreme conditions.

"Even people in the greater Hobart area will be able to see the smoke plume that's coming off this fire."

A smoke alert has since been issued for the greater Hobart area.

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More fires at watch and act

The Pelham blaze took off at 3PM Monday afternoon. ( Supplied )

A fire at Strathgordon in the state's south-west was burning at watch and act on Monday afternoon.

Emergency warnings urging evacuation to Pedder Wilderness Lodge were sent to the phones of people travelling through the Strathgordon area.

TFS chief fire officer Chris Arnol said the forecast damaging winds could affect the agency's ability to respond to existing fires or scout for potential new ignitions.

He said the TFS planned to mobilise aircraft early on Tuesday to search for new fires started by lightning strikes.

"The winds do give us a bit of grief as far as the aviation response goes, so when we get right up the top end ... if we're in that 80 to 90 kilometres an hour [wind] the aircraft can't necessarily fly," Mr Arnol said.

"That does restrict us somewhat, but we've got ample ground crews, we've got strong response."

Much of the TFS response focused on the state's dry East Coast, Mr Arnol said, and he urged Tasmanians to remain vigilant.

"Review your bushfire plan, (and) if you're camping take some informed decisions, think about what you're doing, where you're going to go," Mr Arnol said.

"If in doubt, get out."

Decembers heat records broken

Hot conditions were concentrated on the south of the state today, breaking December records in Hobart.

"The temperature rose pretty sharply this afternoon in Hobart. We managed to climb to as high as 40.8 degrees Celsius at 1:30pm," Bureau of Meteorology forecaster Luke Johnston said.

Severe thunderstorms with damaging winds are approaching the Hobart area. ( Supplied: Bureau of Meteorology )

The previous hottest day in Hobart for December was 40.6 degrees more than 120 years ago, in 1897.

The figure is still subject to verification, but Mr Johnston said it may still get even hotter, with the forecast cold front not likely to affect temperatures until around 7:00pm.

"There's still a chance late this afternoon or early this evening we could go just a little bit higher," he said.

"We're still hovering at just over 40 degrees in the city, so it's not going to cool down quickly."

So far the temperature has fallen just one degree short of the all-time temperature record for the Hobart area of 41.8 degrees in Dunalley on January 4, 2013 — the day deadly bushfires broke out.

Thunderstorm conditions were also forecast for southern Tasmania, with two bands of lightning expected.

Campers not heeding fire warnings

Freycinet National Park is one of Tasmania's parks that have been closed due to extreme weather. ( ABC News: Mitchell Woolnough )

Parks Department acting secretary Jason Jacobi said parks visitors had heeded the service's track closures, including in popular areas such as Freycinet National Park.

However, Mr Jacobi said some campers were failing to adhere to the total fire ban across the state's north and south.

"It's incredibly concerning and disappointing that people aren't aware and alert to the extraordinary risk of doing that," Mr Jacobi said.

Power out and festival closes early

More than 1,000 households are without power, with causes still be investigated.

The forecast has forced the early closure of the Taste of Tasmania festival today.

"In the interest of everyone's safety, we are closing the Taste site at 5:00pm in preparation for the extreme weather front approaching Hobart waterfront at 8:00pm tonight," festival director Brooke Webb said.

The Falls Festival in Marion Bay is going ahead as normal, but the Tasmanian Fire Service (TFS) said contingencies were in place. More than 9,000 people at the Lorne Falls Festival in Victoria were told to evacuate the area on Sunday morning over concerns about fire conditions.

The festival area is surrounded by trees and vegetation, and 30 buses will be on standby to evacuate patrons if a bushfire does threaten the area.