ACT emergency services prepared for the worst when the Bureau of Meteorology issued the warning at about 3pm.

On Wednesday morning, the ACT Emergency Service Agency said crews had been called out to nine jobs overnight, including three trees down. There were also reports trees and branches fallen on the Barton Highway, south of Murrumbateman, had affected traffic flow.

But by sunrise, the storms had eased. While some light showers dusted the capital in the early hours, ahead of a forecast top of 28 degrees, the rain is expected to stay away until Thursday.

A Florey woman, who did not wish to be named, said a branch fell and blocked off part of Tunney Crescent on Tuesday afternoon. Her son had just walked past with their dog when it dropped.

"He could have been killed," she said. The resident said she held concerns about the trees in the street, which were getting old and said that Tuesday's incident was about the "fifteenth time a branch has fallen from one of the broad acres trees".

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ACT fire fighter Mark Welsh was driving to check on his home when he came across what he said looked like a "tornado" from Yass River Road, looking back towards Murrumbateman.

"I was at a friends place helping him with some building and on the Yass River road this massive storm had come up over the hill and hit us, it was unbelieve," Mr Welsh said.

"It ripped trees out left, right and centre."

"I left his place to go back to mine to see if it had got hammered as well and when I got out onto the road and looked back towards where I just came from, I could see the shape of a 'tornado'."

Mr Welsh, who was getting ready for work and a "busy night" said he had never seen conditions like that before.

"The wind was just extreme and when I say extreme it would have had to been in the high hundred wind gusts. It was madness," he said.

"It's really hit and miss with the mountains, so usually when we get storms through here there's always trees down and I guess that's what you get with the bush capital I guess."

Damaging winds of up to 92km/h were detected at Condobolin at 2.40pm, and 98km/h at Parkes at 4pm.

Sydney was also battered by severe storms overnight, losing power to 11,000 homes and businesses across western Sydney and Illawarra.

For warnings visit www.bom.gov.au/nsw/warnings

with Sherryn Groch