A huge damages bill and disruption to the city centre were among the fallout of the storm which forced the closure yesterday of schools, government departments, the Australian National University and the city's biggest shopping precinct.

On the last day of summer, central Canberra was blanketed in ice after the severe supercell storm the type responsible for twisters in the United States' Tornado Alley lashed Civic and northern suburbs.

Hailstones the size of golf balls blocked drains, causing extensive flooding which collapsed ceilings of buildings and left their interiors water-logged.

Canberra Centre, Griffin Centre, Civic Library and the National Sound and Film Archive were all closed yesterday, and school was out for Campbell High School and Canberra Grammar students.

Also closed was the ANU where 70 buildings were damaged and classes have been cancelled until Monday.

Years of climate change research was feared lost, with glasshouses housing experiments at the university's plant culture facility shattered by the storm.

Damage was reported at the CSIRO, ACT Magistrates Court, City Police Station and Winchester Police Centre, as well as government offices including the Department of Employment and Workplace Relations and the National Health and Medical Research Council.

Residents in Braddon, Turner, Reid, Campbell, Cook and Aranda also awoke to damage, with houses flooded and gardens washed away.

The storm struck rapidly, with emergency services fielding calls for help less than half an hour after the Bureau of Meteorology issued a severe storm warning at 9pm on Tuesday.

A bureau spokesman described yesterday the storm as an "ultra-efficient, thermo-dynamic machine" which was rare, with Canberra not experiencing one in at least a decade.

By late yesterday, ACT emergency services had responded to 175 calls, most of which related to flooding and hail damage.

About 40 SES volunteers and 50 firefighters worked around the clock to deal with the damage.

SES crews in NSW were also on standby, with fears of damage from more thunderstorms forecast later in the day and ACT's Emergency Services Agency issued a yellow, or low-level warning.

ESA acting Commissioner David Prince said it had been a difficult storm season.

'The problem is they are all sporadic and erratic we're not quite sure where they're going to hit and with what severity," he said.

"Its too early to tell how this storm compares with previous storms in terms of damage and disruption."

But it had certainly been a bizarre end to summer.

"Its absolutely amazing that people were freezing to death in Civic this morning and certainly the havoc that the road and the car park closures have given us, certainly wasn't what you would think of on the last day of summer," acting Commissioner Prince said.

Cars were stuck in hail which covered roads and driveways, up to a metre deep in some areas yesterday.

Piles of hail were stacked along Bunda Street which was closed as bulldozers worked to clear the ice.

Motorists encountered peak-hour traffic chaos in a city not used to gridlock, with many roads closed including Parkes Way, Vernon Circle and William Hovell Drive.

At a media conference yesterday, acting Commissioner Prince said there was room for improvement in terms of storm warnings to the public, adding that there had been telecommunications problems on Tuesday night.

"We are not happy with the way the warning went we could have got it out immediately," he said.

"Obviously people were concentrating on getting crews out on the road rather than dealing with the warning.

"People can hear thunder, they can hear rain coming but that's not the way we want to operate we want to get warnings out as soon as possible."

Acting Commissioner Prince said it had been fortunate there were no injuries in the storm and there were reports of only two minor collisions on the city's roads.

Fierce storms also hit Sydney's south-west yesterday afternoon, causing flash flooding and injuries from lightning strikes. A man was taken to Campbelltown Hospital in a stable condition after being struck by lightning in Campbelltown.