Lightning strikes and hot, gusty winds fanned more than 60 fires across Victoria on Thursday, including a grassfire which firefighters believe may have destroyed a home in the state's north.

Key points: The wild weather smashed debris into powerlines, leaving thousands without power, and blew a dust storm across Mildura

The wild weather smashed debris into powerlines, leaving thousands without power, and blew a dust storm across Mildura A cool change passed through Melbourne in the afternoon and moved towards the east of the state

A cool change passed through Melbourne in the afternoon and moved towards the east of the state Visit the Vic Emergency website for all of the updated warnings

More than 2,000 firefighters battled out-of-control fires across the state, including a grassfire which threatened homes and lives at Strathallan, just north of Rochester.

At a press conference about 3:30pm, Emergency Management Commissioner Andrew Crisp said firefighters believed at least two structures were lost in the blaze: "It looks as though we've lost a hayshed and possibly another structure and it could be a house."

He said six families had been evacuated from the area.

The Strathallan grassfire just north of Rochester was the most serious blaze firefighters faced on Thursday. ( ABC News )

In a downgraded watch and act warning just after 6:00pm, authorities said firefighters had managed to stop the spread of the blaze and had brought it under control.

Mr Crisp said the blaze was believed to have begun as five separate fires, and police were investigating the cause.

Homes under threat on Melbourne's fringe

Residents at Monbulk in Melbourne's outer-east were under threat from an out-of-control bushfire for several hours on Thursday afternoon, before it was brought under control about 6:50pm.

The "baking oven" weather conditions produced eerie skies across Heidelberg in Melbourne's north. ( Supplied )

A smoke warning was also issued for people in Wantirna South after the Knox Transfer Station waste management facility caught fire.

The smouldering tip was expected to continue to produce smoke for several hours on Thursday night.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 34 seconds 34 s Visibility in the centre of Mildura was poor as a dust storm hit the city.

Lightning strikes sweep state

Mr Crisp said dry lightning strikes had ignited several blazes, including one north of Avoca which was still threatening communities and had resulted in "significant loss of pasture and crop".

Firefighters used 300 trucks and 33 aircraft to fight the fires across the state.

An emergency warning for residents south of the grassfire at Mount Glasgow, north of Clunes, was later downgraded. ( ABC News )

'Baking oven' conditions

The Bureau of Meteorology's Kevin Parkin said the wind gusts and heat that hit Victoria were similar to the conditions faced by New South Wales and Queensland earlier this month.

"It was really like someone had opened the baking oven and hot air ensued," he said.

A small grass fire at Anakie, north of Geelong, was quickly made safe. ( ABC News )

"Fortunately this is just a one-day wonder, we're looking at mild, settled weather tomorrow and across the weekend, so temperatures back to what we would normally expect in November," he said.

Power outages across the state

The strong winds resulted in power outages across the state, with nearly 100,000 Victorians without power about 2:45pm according to power company websites.

There were still about 13,000 people without power by 5:00am Friday.

Powercor said extreme winds brought down more than 18 powerlines across northern and central Victoria, sending 31,000 properties off the grid.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 40 seconds 40 s Dust storms swept through Melbourne on Thursday afternoon.

More than 130 separate faults were also been reported in western Victoria.

An AusNet spokesperson said strong gusts of wind were smashing debris into its powerlines across the state's east as the cold front moved across Victoria.

Dust haze hits Mildura

Meanwhile, the skies in Mildura were turned orange as hot, gusty winds blanketed the city in dust just before 12:30pm.

People stood in the city's main street, Deakin Avenue, capturing footage of the sky.

Dust storms have occurred on a near-weekly basis in Mildura in recent months, with the Millewa region to the city's west in the grip of drought.

Mildura was blanketed in orange as the hot winds whipped up dust. ( ABC News: Christopher Testa )

Dusty conditions were observed across much of the north-west, including at Ouyen, 100 kilometres south of Mildura.

Temperatures soar into 40s

After coming within 0.2 degrees Celsius of its hottest November night on record last night, temperatures in Melbourne soared, hitting 42.2 degrees at Laverton shortly after 1:30pm.

The hot weather started pushing into Victoria through Wednesday night, with overnight temperatures dropping no lower than 26 degrees.

Gusty winds whipped up dust and pollen, as pedestrians in Melbourne donned masks as protection. ( ABC News: Peter Lusted )

"That means we were 0.2 degrees below the all-time November minimum record which was 26.2 degrees on November 25, 1901," the Bureau of Meteorology's Tom Delamotte said.

Temperatures in the state's code red fire danger zones rose steadily over the course of the day, hitting 43.6 degrees in Swan Hill about 1:30pm.

Wild winds tear roofing

Strong winds caused problems in Melbourne's CBD on Thursday morning, where trams were stopped and banked up on Swanston Street.

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The Metropolitan Fire Brigade said a piece of metal roofing fell off a building and caused a power problem with the tram lines.

High pollen count sparks asthma fears

The combination of thunderstorm activity in the state's north and high grass pollen levels also prompted authorities to issue thunderstorm asthma warnings across central, northern and north-eastern Victoria.

In the warnings, people with asthma were urged to keep their reliever medication with them at all times.

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The National Asthma Council Australia also warned that smoke from the fires burning across the state could be putting people's lives at risk.

"Anyone with breathing difficulties needs to take it seriously and act immediately," the council's chief executive Siobhan Brophy said.

The code red warning, which is equivalent to the "catastrophic" fire rating in other states, applied to the parts of the state that include the cities of Swan Hill, Mildura, Bendigo and Shepparton.

The Koorlong Primary School is closed today because of the threat of fire. ( ABC News: Christopher Testa )

Dozens of schools and childcare centres in north-western Victoria were closed because of the threat of fire.