A TOTAL fire ban has been declared statewide and danger ratings upgraded as Victoria braces for temperatures of up to 44C tomorrow.

No fires can be lit in the open air from midnight as emergency crews prepare for a scorcher, and the longest stretch of extreme heat since 2009's Black Saturday.

An "extreme" fire danger rating has this afternoon been issued for the Wimmera, South West and Central regions.

The danger is "severe" elsewhere.

It comes as an uncontrolled blaze threatens the historic Tasmanian town of Richmond with residents being urged to leave immediately.

Fire crews had to battle two fires tonight . A worker was injured in a flash fire that created to a chemical hazard at a factory in Melbourne's north and CFA fire fighters brought a fire in a storage facility under control in Melton.

Country Fire Authority state duty officer Tony Bearzatto urged Victorians to have their bushfire survival plans ready and to monitor conditions.

He warned residents trying to complete last-minute burn offs that the opportunity had now passed.

"They should not be burning off," Mr Bearzatto said.

"Keep it for another time when the conditions are more favourable."

Firefighters have been battling a handful of grassfires today but all are under control.

Emergency authorities are completing last-minute preparations.

Mr Bearzatto said this morning about 8000 firefighters from the CFA, Department of Sustainability and Environment and Metropolitan Fire Brigade were on standby.

Forty aircraft, including two aircranes, are also ready to be called into action.

He said while no total fire ban had been declared in Victoria today, most regions had fire restrictions.

Temperatures had climbed into the mid-30s in many areas of the state's west by 4pm. Horsham peaked at 39.2C at 4.21pm, but had dropped back to 37.9C at 6pm, while Mildura reached 40C at 5.05pm, before cooling off slightly to 38.6C an hour later.

Melbourne hit a high of 37.1C by 4.30pm - only dropping to 36.3C at 6pm - after staying relatively cool for the morning.

Mr Bearzatto urged Victorians to avoid doing anything that might spark a fire, particularly farmers using machinery for harvesting.

"Today's very hot statewide, with fire danger ratings high to very high in most parts of the state," he said.

"Tomorrow we're expecting hotter and drier and windier conditions with extreme fire danger ratings in the southwest and the Wimmera area, which is the first for the season, and severe fire danger ratings for the rest of the state, except east Gippsland."

Fire Services Commissioner Craig Lapsley has warned Victorians to stay alert as the danger intensifies, but insisted the state was in a strong position should an emergency arise.

"The fire services are well prepared, well equipped, and ready to go," he said.

Tomorrow is shaping as the day of greatest risk.

The heatwave tomorrow will force Australia's best road cyclists to get out of bed two hours earlier.

Stage one of the Herald Sun Tour, following today's opening prologue in Williamstown, will start at 9.30am instead of 11am to protect the riders from the worst of the day's conditions.

Another event, a junior lifesaving carnival at Torquay, for more than 1200 competitors and their families, has been postponed.

Mr Lapsley said strong northerly winds of up to 50km/h, bringing "superheated" air from central Australia, posed a significant fire threat.

"The northern winds are the hot winds and obviously are more fierce," Mr Lapsley said.

"That's why Friday is a critical day. Wind is the driving force of how fires move fast."

State agency commander Darrin McKenzie said the work, begun in July, aimed to protect towns and critical infrastructure.

"Strategically it's very useful to slow or stop the progression of fires," he said.

Victoria's northwest is expected to cop the brunt of the hot blast - some experts are tipping extreme temperatures for at least nine days straight.

Weather bureau senior forecaster Dean Stewart said Mildura should expect maximums of 40C or above until at least Tuesday.

It would be the longest heatwave since early 2009, when Mildura recorded 12 consecutive days above 40C.

"It's shaping up to be the longest spell of above 40C days since Black Saturday, but it's nowhere near those kind of conditions at the moment," Mr Stewart said.

A cool southwesterly change should bring relief to southern Victoria late tomorrow, but it will be short-lived.

STAY SAFE

The Herald Sun has joined with fire authorities to keep Victorians informed. Check out the Bushfire Ready page for the latest advice, warnings and videos from the CFA. This page is updated with the latest warnings from across the state. Save it to your bookmarks. You can access it from our homepage (click on Bushfire Ready) from any computer. This service is not available on smart phones.

Check live weather information - including fire warnings - on your computer AND smart phone at our Weather page. Just add m.heraldsun.com.au to your smart phone bookmarks and follow the View weather forecast link.

The CFA has a live fire map. Check it out here and add to your bookmarks.

The Herald Sun will keep you informed throughout the heatwave. Check back regularly for weather information, reader photos and fire warnings on your PC and mobile. Reports and alerts will also be posted to our Facebook page and from our official Twitter account.

Meanwhile, lifesavers are on alert as thousands head for the beach to escape Victoria's searing heat.

Seaside holiday spots and city beaches are expected to be packed as a heatwave grips the state.

Many will also flock to waterways inland.

Life Saving Victoria general manager Paul Shannon urged beachgoers to only swim at patrolled locations and stay between the flags.

"If our lifesavers can't see you, they can't save you," Mr Shannon said.

More than 100 people have been rescued this season and about 380 given first aid.

Mr Shannon said it was vital to never swim alone, always ensure children were supervised and understand the dangers. "It's important to remember that all beaches are inherently dangerous, even those in the bays or those that appear calm," Mr Shannon said.

Lifeguard services run every day in the school holidays at beaches including Torquay, Inverloch and Ocean Grove.

The state's electricity grid will also be put to the test in the coming days as residents scramble to keep cool in the sweltering temperatures.

Once considered a luxury, airconditioner sales have jumped in the past decade, putting extra pressure on electricity supplies across the country.

But service providers CitiPower, Powercor and SP Ausnet believe there is a sufficient electricity supply to prevent the brownouts and blackouts experienced during previous Melbourne summers.

The State Government will receive regular updates on electricity demand and supply from the Australian Energy Market Operator across the weekend and believes there is no anticipated threat to supply.

Despite this, residents have been advised to take simple steps which can minimise pressure on the grid.

The Energy Supply Association of Australia recommends adjusting thermostats to 24C and to turn units on early, as airconditioners operate more efficiently when the outside air temperature is cooler.

For fire danger information, visit cfa.vic.gov.au or phone the Bushfire Information Line, 1800 240 667.