A large eucalypt blown down near the Mona Vale shopping centre.

A large eucalypt blown down near the Mona Vale shopping centre. Photo: Wolter Peeters

Sydney’s north and northern beaches have borne the brunt of wild weather on Sunday afternoon with residents reporting tornado-like scenes and widespread blackouts.

About 20,000 homes and businesses from Palm Beach to Freshwater lost power around 1pm.

By 9pm, power had been restored to most homes on the northern beaches however Ausgrid reported that 3000 homes were still without power in Warriewood, Duffy's Forest, Church Point and Bayview.

Storm damage along McCarrs Creek Road in Terrey Hills.

Storm damage along McCarrs Creek Road in Terrey Hills. Photo: Steven Siewert

"There is quite a bit of damage to the network, we've seen whole trees coming down, a lot of falling branches taking out wires and some lightning strikes,’’ said an Ausgrid spokesman on Sunday afternoon.

"We have crews working at multiple locations and power will be restored gradually. It will be well into the late afternoon and early evening until we have power back in all areas."

The storm lasted for under an hour in most areas but brought flash flooding, winds of up to 100 km/hr and falling trees.

Bathers make a run for it as a severe storm bears down on Newport, on Sydney's Northern Beaches on Sunday.

Bathers make a run for it as a severe storm bears down on Newport, on Sydney's Northern Beaches on Sunday. Photo: Nick Moir

Power lines and trees fell on Pittwater Road in Mona Vale and around Duffy’s Forest and Terrey Hills.

Traffic lights were blacked out in several spots, according to the Live Traffic NSW website.

As the storm moves north to the central coast, Ausgrid has reported 1900 homes at Wyoming and Lisarow without power.

Weatherzone: NSW storm tracker



'Really flying'

The storms, though, were driven by strong winds, with speeds of as much as 100 km/h and didn't last long.

Ben McBurney, a meteorologist at Weatherzone, said the northern suburbs were the hardest hit, with wind gusts reaching 89 km/h at Terrey Hills at about 12.30pm and rainfall totals of about 10 millimetres.

A fallen tree at Duffy's Forest on Sunday afternoon.

A fallen tree in Duffy's Forest on Sunday afternoon. Photo: @Ausgrid Twitter

“They’re really flying, and they’ll be over before you know it,” Mr McBurney said, adding that the storm activity was expected to be over by about 2pm for most of Sydney.

“There is the risk of very brief flash flooding but generally the storms are moving so fast moving that while the rain will be heavy briefly, it’s just not going to last long enough to have big totals accumulating,” Mr McBurney said.

The Bureau of Meteorology has updated a severe thunderstorm warning, shifting the area of risk from north of Sydney almost to the Queensland border, and inland to Bourke.

"Severe thunderstorms are likely to produce large hailstones and damaging winds in the warning area over the next several hours," the bureau said. "Locations which may be affected include Grafton, Coffs Harbour, Port Macquarie, Taree, Gosford, Armidale, Tamworth and Moree."

Wind speeds of as much as 137 km/h were earlier recorded at Thredbo in the state’s south-east.

By 2pm, SES volunteers has been called to 120 jobs mainly around the northern beaches and spokesman Todd Burns predicted that number would rise to 300 by the end of the day.

"This storm has hit Sydney so quickly, all our volunteers have just had to scramble together to get each job covered as quickly as possible," he said.

One of biggest jobs is a tree which came down on a parked car on Mona Vale Road.

Mr Burns says SES volunteers are using the break in the weather to "get on top" of existing jobs in the Northern Beaches area, however he warns that Sydney could receive another hit of bad weather before the day is out.

"When the storms are popping up this quickly, it’s hard to predict when the next one will hit," he said.

Raining on the parade

The wild weather hit as several outdoor events kicked off in Sydney, with the St Patrick’s Day Parade making its way through the central business district to end at Hyde Park at around 1pm.

March in March protesters, meanwhile, are gathering at Belmore Park, with speeches due to start at 1.20pm and a march to Victoria Park due to begin at 3pm.

It was a sea of green but the black stuff was what really mattered as thunder storms sent St Patrick’s Day revellers scurrying for early drinks.

Hundreds of people flooded into Sydney’s CBD early on Sunday morning to kick-off the annual St Patrick’s Day celebrations with a march through the city and a free concert.

The day started sunny and warm, to be sure. But heavy rain and thunder storms soon forced some party-goers to dive for cover.

That was a fortunate turn of events for the city’s pub landlords, many of whom were doing a brisk trade, as thirsty revellers settled into cosy nooks and downed a the classic Irish bevy Guinness.

‘‘Doesn’t matter what the weather does, we’ll still celebrate - the spirit of St Paddy lives on,’’ one sozzled reveller dressed as a leprechaun told AAP.

Hyde Park on Sunday morning was alive with music and people bedecked in green hats, green t-shirts, green pants ... green everything.

The St Patrick’s Day Parade still kicked-off at Bathurst Street at noon - despite the rain - and wound its way through the city to Hyde Park.

‘‘The great thing about Paddy’s Day is that you really don’t have to be Irish to enjoy it,’’ reveller Lisa Franklin told AAP.

Indeed, it wasn’t just members of Sydney’s big Irish population present, with children and adults of all backgrounds getting the party started.

St Patrick’s Day is not actually until Monday but festivities are being staged across the city for several days.

Weatherzone is owned by Fairfax Media, publisher of this website.

with AAP, Rachel Olding and Brittany Rupert