Hailstorm 'roared like a jet', and disappeared in a flash

Fifty minutes after the temperature peaked at 27 degrees at midday, skies were dark in the city.

It took a few seconds for hail the size of golf balls to start battering buildings and cars about 12.50pm, cutting north-west to south-east from Belconnen to Fyshwick.

Michael Southam was working in the John Gorton Building at Parkes as skies darkened and wind gusts reached 117 km/h at Canberra Airport.

"Within a matter of 15 minutes it almost became like night time, that's how dark it was," he said.

The Department of the Environment and Energy staff member watched from inside the building as hail fell thick, cracked its windows and damaged cars outside.

"There wasn't a car without a scratch and a window broken," Mr Southam said.

"It just happened so quickly."

Mr Southam walked outside the John Gorton Building after the deluge cleared and found the ground so thick with hail stones and leaves shredded from trees he couldn't find the path.

"I stood there for a second trying to remember where the car park was."

In less than 10 minutes the storm smashed cars and damaged buildings across the parliamentary triangle.

People inspected their heavily hit cars in the car park next to the John Gorton Building later on Monday afternoon.

One public servant who didn't want to be named said her Kia Sorento was a write-off.

The sunroof and windscreen were shattered and heavy rain had drenched the inside of the vehicle.

The roof had collapsed with the impact of countless hail stones the size of golf and cricket balls.

"Every single panel has been damaged," she said.

Environment Department and Bureau of Meteorology staff working in Parkes went home early following the storm. Treasury public servants were encouraged to leave if they had to deal with storm damage to their car or home.

The storm also forced the Museum of Australian Democracy to close early.

Hail fell heavily at ANU, forcing the university to close its Acton campus on Monday afternoon and Tuesday to all but essential staff and those staying in residences while it assessed the damage to buildings.

Weatherzone meteorologist Graeme Brittain said a combination of moisture near the earth's surface and converging winds brought on the hailstorm.

A trough had dragged the moisture over the region from the Tasman Sea. Converging winds pushed the air up and triggered the storm.

Small IT business owner Christopher Perkovic had just exited his car in Fyshwick while on the job when the hail stones began to fall, stinging as they hit him on the head.

"That's when I could start hearing this roaring sound," he said.

"The roaring got louder and louder, and it absolutely barraged everywhere."

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He found cover in 20 seconds, and edged against a wall as hail stones fell at an angle and hit his legs.

The stones reached almost the size of a tennis ball in size and bounced into the building as he finally opened the door inside.

"My head's still pretty sore, I can feel where it hit in the centre," Mr Perkovic said.

Hail hit Belconnen suburbs, where Marites Moore waited inside her Dunlop home as the storm raged.

"Just before the hail came, gale force winds came through," she said.

One gust blew so hard it opened a hard-to-open gate at the home. Hail stones began to hammer the building and damage her pergola roof.

Combined with the strong wind, the hail appeared to fall almost horizontally at one point.

She described the hail's noise as like "the roar of a jet engine".

"You actually couldn't hear anything else, it was that loud.

"It was really noisy, and it got really, really cold. That was the thing I really noticed."

The storm passed nearly as quickly as it started, heading south and east of the ACT over the Southern Tablelands towards the coast.

- with Steve Evans