From rain and hail pelting recently razed firegrounds, to a fast-moving dust storm blocking out the sun in western New South Wales, the weather across parts of Australia over the past 24 hours has been extreme.

The wild storms represent a stark contrast to the bushfires that have been raging since October, bringing orange skies and a choking haze to eastern cities.

While firegrounds across NSW and Victoria have been sent some much-needed rain, locals now have to worry about flash flooding, which could be complicated by debris run-off from recent fires.

First, storms and hail hit Melbourne

Storms began in parts of suburban Melbourne and southern Victoria on Sunday afternoon, when golf-ball sized hailstones rained down amid severe thunderstorms which brought damaging winds and heavy rainfall.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 59 seconds 59 s Melbourne suburbs were hammered with golf ball-sized hailstones on Sunday.

The storms — warned by BOM to be the "wettest two-day period in many, many months" — had authorities worried debris from recently-burnt vegetation would sweep into waterways and onto roads and cause landslides.

Victorian emergency authorities said the rainfall caused flash flooding across parts of Victoria and caused significant damage in Melbourne.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 38 seconds 3 m 38 s Destructive hail hits the country's capital during a severe thunderstorm.

An ominous dust storm left towns in daytime darkness

On Sunday night, residents in NSW's west were hoping for rain, after a promising forecast from the Bureau of Meteorology.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 21 seconds 21 s Grace Behsman captured this video as she almost drove into a dust storm.

Instead, the region experienced one of the worst dust storms to date.

A view of the dust storm as it descended on Trangie, west of Dubbo. ( Supplied: Jackie Cantrall )

The dust storm spread from Broken Hill across to Nyngan, Parkes and Dubbo, leaving towns in darkness.

Residents watch in shock as a monster dust storm approaches. ( ABC Western Plains: Jen Browning )

"The dust storm was moving fast and was so thick that it went completely dark, [resulting in] zero visibility in less than a minute," Dubbo resident Jenny Duggan said.

A wind gust of 107 kilometres per hour was recorded in Dubbo at 7:45pm.

But after all that, only 2.2 millimetres of rain fell in Dubbo.

Giant hail battered Canberra

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 1 m A summer hailstorm smashed cars and buildings in Canberra.

The hailstorm which hit Canberra at lunchtime on Monday lasted just 10 minutes, but left a trail of destruction: smashed windows in houses and cars, trees felled or torn to shreds, dozens of powerlines down, and two people injured.

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At the storm's peak more than 3,000 homes were without power.

The Canberra hailstorm on Monday at lunchtime lasted just ten minutes. ( ABC News: Matt Roberts )

Emergency services received a record 1,300 calls for help, and BOM reported wind gusts of 116 kph.

Acting head of the SES Geoff Butler said he believed it was the highest number of calls ever received by the agency.

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"It's certainly a very high number, I think the highest number I'd heard of before that was around 600 jobs from a storm, so we've pretty much doubled that," he said.

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Less than two weeks ago, Canberrans suffered through days on end of glaring orange skies and some of the worst air quality in the world.

Paramedics treat the 16-year-old boy struck by lightning at Echo Point. ( ABC News )

Two tourists were struck by lightning in NSW

As Monday's storm cells moved east, a pair of tourists were struck by lightning near Echo Point at Katoomba in the Blue Mountains National Park.

A 16-year-old boy was left with entry and exit wounds to his arms and feet and burn marks on his torso, while a 24-year-old sustained an electric shock while leaning against a metal pole.

Both were taken to hospital in a stable condition.

At the same time, storms delivered much-needed rain to firegrounds in the Snowy Mountains and South Coast.

Hailstones the size of golf balls pelted Sydney and there were reports of power outages.

With a bit of rain, some fire-ravaged regions begin recovery

But it's not all bad news — rain has brought new life into areas scorched by fire only weeks ago.

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Actor Russell Crowe, who has been instrumental in raising funds for bushfire relief and has been fighting fires himself, posted two comparison images of his farm near Coffs Harbour, taken 10 weeks apart.

The area appeared totally rejuvenated after this weekend's heavy rain — a striking transformation that may give hope to other fire-battered regions around the country.