Softball-sized hailstones hit Brisbane

Hailstones the size of a softballs rained down on Brisbane's south and southwest suburbs during the height of the thunderstorm that swept through the city on Sunday.

The Bureau of Meteorology said there were reports of hailstones 9cm in diameter falling during what it described as a "dangerous thunderstorm", which shut down Brisbane Airport for a short period.

Forecaster David Grant said hailstones 4-6cm in diameter also had been reported in the west and inner west of the CBD.

It was the second consecutive day for Queensland's southeast being battered by ferocious storms.

Power company Energex said the storms had knocked out electricity to more than 100,000 homes and businesses over the weekend.

More than 18,000 homes and businesses were still without power on Sunday when almost 25,000 lightning strikes were recorded, with many hitting the electricity network.

Many of the lightning strikes occurred when a storm raced through the Moreton Bay and Sunshine Coast council areas early in the afternoon and in a separate storm hitting the Logan, Brisbane and Moreton Bay council areas.

Energex asked southeast Queenslanders to remain patient while crews worked to restore power as quickly and safely as possible.

Qantas cancelled three out of four flights to Sydney on Sunday, leaving hundreds of passengers stranded.

They advised Brisbane-based passengers to return home while they promised to find hotel rooms for about 300 other passengers who would not be flying out.

One passenger told AAP the storms that swept through were very fierce, causing the airport to shut down operations for at least 30 minutes.

Virgin had to divert three flights flying into Brisbane on Sunday with two going to Rockhampton and the other to Coolangatta, where passengers were put on buses.

It also cancelled five flights out of Brisbane where the planes would not have been able to reach their destination city - such as Sydney and Adelaide - before curfews took effect.

Emergency Management Queensland advised people to move their cars under cover and away from trees, not to attempt to drive, walk or ride through flood waters and avoid using the phone during a thunderstorm.

The Department of Community Safety told AAP at least 160 calls had been received on Sunday, to help with minor flooding, leaking roofs and tarping.

At about 7pm (AEST) fans at Brisbane's Harvest music festival had to be evacuated because of the hail, with music lovers taking to Facebook to express their disappointment.

International acts such as Santigold, Grizzly Bear and Sigur Ros were due to take the stage at the festival, which was held at the Brisbane Botanical Gardens.

"We just got evacuated from Harvest Festival... All the good bands were about to start", said Brooke Baldock of the Gold Coast.

Amy Chambers, who lives in the inner-city suburb of Dutton Park, said Sunday night's storm was sudden and violent.

"There are a lot of trees and tree limbs down," she said.

"The rain was coming down horizontal and there was hail about the size of a dollar coin. I've heard it was much bigger in other parts."

Ms Chambers said the wind blew so hard it forced her front door open.