Tasmanian Fire Service has issued an emergency warning alert for the fire on the Tasman Hwy, Bicheno.

THE major fire at Bicheno in Tasmania's east has been downgraded and the Tasman Highway has been reopened.

The Tasmania Fire Service (TFS) has issued an ''advice'' alert level for the fire, which was earlier classified at an emergency warning level.

The TFS says the fire danger rating in the area is low to moderate, and there is no immediate threat to communities.

The Tasman Highway has been re-opened and motorists are being urged to be cautious due to possible smoke and emergency services vehicles in the area.

The fire is still not under control and authorities say people may experience embers, smoke and ash falling on Coles Bay Road, south of Apsley River, and the Tasman Highway, south of Bicheno.

Back burning off the Cole Bay Road will continue through the night and residents are advised that they should not be alarmed if there is more smoke in this area.

Earlier, the fire at Forcett, east of Hobart, was downgraded to a watch and act level as cooler weather spread across the island state.

The Forcett fire, which has scorched about 15,000 hectares, was earlier classified at an Emergency Warning level.

More than a dozen properties have been lost south of Bicheno, with more than a 100 feared lost overall.

Victoria was planning to send 65 firefighters to help tonight.

Thousands flee areas of Tasmania as fires spread

The Tasman Peninsula fire claimed at least 80 properties and left thousands of people isolated yesterday night.

Police and commercial boats were being used to ferry in supplies and ferry out people most in need.

No deaths or serious injuries have yet been confirmed, but Deputy Police Commissioner Scott Tilyard earlier said a team was on the ground at Dunalley to investigate a fire crew's concerns that a man may have been trapped while trying to defend his house.

Prime Minister Julia Gillard said the federal government was supporting the fire effort.

''We are working with the state government to support people and make sure that they get through,'' Ms Gillard told ABC radio.

''My message is there's only one you.

''Everything else in life at the end of the day, no matter how precious, can be replaced.

''What can't be replaced is a human life.''

Insurers declared the bushfire-hit towns a catastrophe and police powers were increased when the Tasman Peninsula was declared a serious-incident site.

The Insurance Industry Council of Australia's declaration included the towns of Dunalley, Connellys Marsh, Forcett, Copping, Murdunna, Boomer Bay, Primrose Sands, Susans Bay, Eaglehawk Neck and Taranna.

Electricity company Aurora told people whose power had been cut off to expect delays of several weeks before it was restored.

About 300 poles were down on the Tasman Peninsula.

Property losses from the peninsula fire have been huge, with 30 per cent of the buildings in the small community of Dunalley, 55km southeast of Hobart, destroyed.

These included the school, police station and bakery.

At Connellys Marsh, 40 per cent of the buildings are gone, including three houses at Copping and several at Primrose Sands.

Twenty houses have been lost around Murdunna.

Several thousand people, many of them tourists, are stranded with access roads closed.

Around 700 are taking refuge at the Port Arthur historic site, another 2000 at a community centre at Nubeena and more than 50 at the Dunalley pub.

And a flotilla of boats is the lifeline for thousands of people stranded on the Tasman Peninsula as bushfires continue to rage out of control.

Recreational and commercial vessels are being used to bring in thousands of meals and other essential supplies and to evacuate people most in need.

Police said today that 600 people, many of them visitors to the area, were set to spend a second night at convict ruins.

There were 2000 people at a temporary refuge in Nubeena and another 100 at the Dunalley Hotel.

The road into the peninsula, the Arthur Highway, has been closed since Friday.

Boats delivered 3000 meals as well as fuel, water and health workers.

A generator was being sought as power is out in much of the area.

Acting police commissioner Scott Tilyard said he was hopeful some vehicles could be escorted from the peninsula.

He said tourists were obviously keen to get out.

It had been ''a long night for many people but the main thing is that they have been safe'', he said.

Up to 1000 people were reported to have been taken out by boat overnight, but police could not confirm the number.

''I would imagine there'll be numerous stories about the heroic and risky approaches that were taken out there,'' TFS chief commissioner Mike Brown said.

No deaths or serious injuries have been confirmed.

A fire in the Derwent Valley northwest of Hobart was affecting the communities of Ellendale and Karanja, but the extent of property damage was unknown.

Conditions across southern Tasmania today were cooler than yesterday, when Hobart reached 41.8C - its hottest since record keeping began in 1883.

State fire chief Mike Brown said similar conditions in 1967 had resulted in the loss of 2000 homes and 62 lives.

''I would imagine there'll be numerous stories about the heroic and risky approaches that were taken out there,'' he said.

''The big outcome for us ... is that at the moment there looks to be no loss of life or injuries.''

He said this was because of the way ''we put out our warnings, and clearly a lot of people did heed those warnings''.

People concerned about relatives and friends can call a police hotline on 1800 567 567.

SA prepares for continued threat

A number of total fire bans have been implemented across South Australia.

The bans will be in place tomorrow in the Northwest Pastoral, Northeast Pastoral, West Coast, Flinders, Mid North and Yorke Peninsula districts.

Today, 50 fire crews controlled flare-ups from a controlled bushfire on South Australia's Fleurieu Peninsula as the threat of more fires across the state eased.

A bushfire at Finniss was brought under control late on Friday night, with firefighters remaining in the area to control flare-ups.

Adelaide sweltered through its fourth-hottest day on record yesterday, while temperatures soared past 48C in some parts of the state.

CFS state co-ordinator Malim Watts said people needed to remain vigilant.

Total fire bans have been issued in three districts today, with severe fire conditions forecast in the Northeast Pastoral, Northwest Pastoral and Flinders districts.

The Bureau of Meteorology said temperatures in Adelaide would drop to the low 30s on Saturday but forecast a return to very hot conditions for most of next week.

Victorian fire latest

A body has been found following a house fire near Kerang in northern Victoria.

Firefighters were called to a house on Kerang-Murrabit Road at Capels Crossing just before 4pm (AEDT) today and were searching debris when they found the body.

Police and fire investigators are examining the scene.

Meanwhile, Victorian firefighters are making the most of cooler conditions as they battle to bring two out-of-control bushfires within containment lines.

A total of 38 trucks and several aircraft were at the scene of a major bushfire at Kentbruck, in the state's southwest today.

The blaze northeast of Portland, between Port Fairy and the small town of Nelson next to the South Australian border, ignited about 18km southeast of the Mt Richmond National Park along the Princes Hwy yesterday afternoon.

It burned more than 2000 hectares.

No property is under threat, but smoke from the fire is visible several hundred kilometres away.

State Control Centre spokeswoman Sonia Maclean said no homes or property were threatened by the fire, and aircraft account of the scene overnight had revealed the blaze was tearing through the pine forest and had swelled further than the 1200ha circumference initially reported.

A precautionary advice message was issued to Portland residents and nearby communities earlier this morning.

"Coming into the daylight, aerial crews have been able to establish a better indication of the fire and it appears it is across 2000ha, but it has also spread quite quickly," she said.

"The issue in fighting this tricky fire is that the ground is wet and quite boggy so firefighters are using an air-focused attack.

Smoke sightings of the inferno have been reported from as far away as Hamilton, about 85km northeast of the blaze.

CFA spokesman Chris Clugston said campgrounds Lake Monibeong and Swan Lake were evacuated and the Cobboboonee National Park was closed.

Meanwhile, residents of Ensay, in East Gippsland, were told to remain vigilant as a blaze burned out of control around 7km north of the town.

A CFA spokeswoman said crews hoped to have both fires under control this afternoon.

''The crews on the ground are putting measures in place to create containment lines and are doing some backburning,'' she told AAP.

No new bushfires were recorded today.

Temperatures today were much cooler than Friday, when the mercury peaked above 40C across much of the state.

Work was also under way to restore Victoria's Country Fire Authority website to full capacity.

The crash occurred as the state sweltered through its hottest day in several years. At some points up to 700 people a second tried to access the website and FireReady App.

In a statement late on Friday, Victoria's fire services commissioner Craig Lapsley said he had asked CFA chief Mick Bourke to investigate why some people were still experiencing delays on the website.

Mr Lapsley said the CFA would work throughout the weekend to respond to the issue as a "key priority".

"We recognise it has been frustrating for people who rely on the website and app for fire information," he said.

"Seeking out the appropriate information is exactly what we have been asking the community to do and we know people are relying on this technology to keep themselves updated about their fire risk."

The capacity of the website and the FireReady App were increased after the crash.

Mr Lapsley says important fire information is also available from ABC radio, SKY NEWS, and CFA social media channels such as Facebook and Twitter as well as the Victorian Bushfire Information Line on 1800 240 667.

NSW fought bushfire 'deliberately lit'

The NSW Rural Fire Service has established total fire bans in the northern and southern Riverina districts and the lower and upper Central West plains.

The bans come into effect from midnight and end midnight Sunday.

A fire service spokesman said the fire risk would ease on Monday but would again escalate on Tuesday.

Today firefighters fought a blaze on the mid-north coast in the Booti Booti National Park near Forster, forcing the closure of roads in the area and isolating the town of Green Point.

The fire has been brought under control.

Teens charged over another arson attack

Specialist crime scene officers and Fire Investigators from the Rural Fire Service will examine the area today to pinpoint what caused the fire, which are being treated as suspicious.

Police from Manning Great Lakes are appealing for public assistance as they continue their inquiries into the incident.

All roads have now been reopened.

But while the heat records tumbled across the country - including Thursday's 48.2C scorcher in the Nullarbor border town of Eucla - only sea-breezy Sydney was bringing the nation's average top temperature down.

Sydney city hit a high of just 26.6C yesterday, and 34C in the west, compared with peak temperatures of 45.1C in Wilcannia and 45C in Bourke in the state's far northwest.

SE Queensland escapes worst of heat

Southeast Queensland escaped the brunt of the heatwave, but areas to to the west were not so lucky.

Locals in the western Queensland town of Birdsville reported the 47.3C temperatures made it too hot to even go to the pub for a thirst quencher.

Brisbane and the Gold and Sunshine coasts recorded temperatures of around 30C, but Weather bureau senior forecaster Michelle Berry said temperatures in the west soared to 7C above average.

"We were one of the cooler capital cities," Ms Berry said.

"Many other capitals had a very hot day, but Brisbane had mild temperatures."