SYDNEY, Jan. 21 (Xinhua) -- A mammoth clean-up has been underway since Tuesday after freak thunderstorms lashed Australia's east overnight, leaving around 30,000 homes without power.

Rolling through Canberra in the afternoon, the monster storm system that saw golf-ball-sized hailstones batter the national capital, continued further east as the evening went on hitting large parts of New South Wales (NSW), Queensland and Victoria.

According to the NSW State Emergency Service (SES), there were more than 800 calls for assistance overnight, with most coming from Sydney's southern suburbs.

"Predominantly it was for downed trees," NSW SES Director of Operations Paul Bailey told Sky News.

"But we also had a few very serious incidents where trees had fallen on cars with people in them. Those people were rescued from those vehicles and luckily they were not terribly injured."

"We also had a lot of leaking roofs because there was some significant wind associated with this storm and it did tear a few roofs off."

With gusts clocked at over 100 km per hour in some parts, dramatic vision uploaded to social media showed sections of roof from the Bringelly Village Shopping Centre in Sydney's west flying through the air and smashing into traffic on a main road.

In the Blue Mountains region, two males aged 16 and 24, were struck by lightning in separate incidents. They are both in a stable condition recovering in hospital.

Although the storm cells were extremely powerful, Bureau of Meteorology Forecaster Abrar Shabren told Xinhua that the inland troughs which caused the wild weather are actually quite common in the summer months Down Under.

"The usual weather pattern that we have at this time of the year, that's triggering these inland troughs which are developing moisture, forming convective clouds, and that's why we're seeing a lot of thunderstorm activity," he said.

Further north in Queensland, that thunderstorm activity brought a total of 44,000 lightning strikes, which left around 20,000 homes without power.

Likewise in NSW, electricity generator Ausgrid said, 14,000 homes lost power due to the strong winds, lightning and hail.

But on Tuesday morning, the company said, "less than 4,000 customers remained without power."

While the storm caused a huge amount of destruction resulting in 320 million Australian dollars (220 million U.S. dollars) worth of insurance claims according the Australian Newspaper, for some communities facing the threat of bushfires, the wet weather was a welcome sight.

In the first week of January, there were around 150 wildfires burning across the east coast, at the moment there are only 80.