Lismore on the New South Wales north coast has been declared a natural disaster zone after hailstorms left a path of destruction on Tuesday, local reports said.
The State Emergency Service was preparing for further damage on Thursday as more electrical storms were expected in the region.
The State Emergency Service (SES) crews have received about 470 calls for assistance, and an extra 15 SES teams arrived in the Lismore area on Tuesday night and on early Wednesday to help deal with them.
Hailstones smashed homes and cars during the tempest on Tuesday. They also destroyed nearby macadamia plantations.
"It was amazing, the wind came up very quickly and left quickly but it was like a mini tornado," one local resident told Channel 7 on Wednesday.
Lismore Base Hospital reported that 21 people were injured during the storms.
"I was under the table with the dog", another local said.
Churches and police stations were damaged and one school lost 100 windows.
A young boy gave his account of the storm saying "you couldn't see across the road because it was full of like rain and hail."
Helicopters were being used on Wednesday to inspect the area and determine clean-up priorities.
The Bureau of Meteorology forecaster said there was the chance of a storm on Wednesday but that Thursday and Friday were more likely to see intense weather in the Lismore area.