Wildest winds in three years

WILD weather is smashing Australia's east coast with, in some areas, the fiercest gusts seen for three years.

Scores of flights have been delayed at Sydney Airport and gusts of more than 100km/h buffeting the city's harbour.

The winds have already exceeded the worst expectations of forecasters.

More than 40,000 homes across Sydney and the Central Coast have been hit by power outages, roofs have been ripped off buildings and the NSW State Emergency Service say they have been flooded with calls.

Rail services have also been hit with a tree on the line at Canterbury and objects blown onto overhead wires at Strathfield delaying the T1 Western and North Shore, T2 Inner West and South and T3 Bankstown lines.

At least 120 flights at Kingsford-Smith have been cancelled and many more delayed. Into the afternoon flights continue to be disrupted with some services to Melbourne, Brisbane, Cairns and Canberra axed on all major airlines.

Travellers have been advised to check with their individual airlines amid warnings that further delays are likely to occur as the wind gusts pick up later today.

It comes as a looming cold front is set to send temperatures plummeting across southeastern Australia.

Earlier on Friday, the Bureau of Meteorology (BoM) advised that a large swath of NSW, from the north of Newcastle all the way south to the Victorian border would be affected by severe winds.

Sydneysiders were warned to brace for 90km/h gusts. But, at 11.30am, a wind speed of 106km/h was reported on Sydney Harbour, it's strongest gust for 12 months. At Kurnell, in southern Sydney, a gust of 102km/h was recorded right in the flight path of the city's airport, that's the highest wind speed recorded in that location for three years.

Sydney Airport itself recorded a gust of 95km/h just after midday.

Sydney mum Amy shared with news.com.au her family's experience of the wild conditions. A trip to the city's Centennial Park turned into a weather assault course for her five-year-old son with is his hair whipped up by the gale force winds.

Sky News Weather meteorologist Tom Saunders told news.com.au a cold front is moving north from Victoria which will cause winds to turn even cooler south-westerly tonight.

"Ahead of the front snow has already fallen in Oberon and should descend to 900m on the NSW southern and central ranges tonight," he said.

"Snow is predicted down to 600m in Victoria and 300m in Tasmania. Over 50cm has fallen across the Alps over the past 48 hours after heavy rain earlier in the week."

Mr Saunders said the wild winds hitting NSW were caused by a vigorous westerly airstream which has developed between a high over South Australia and a deep low in the Tasman Sea.

"The winds are gale force today along the NSW central and southern coast and ranges and will remain strong to gale force through Saturday," he said.

"Gale force refers to winds averaging over 62km/h with gust over 90km/h is equivalent to a Category 1 tropical cyclone. Winds of this strength can cause minor damage to property and can down trees."

Winds of 104km/h were recorded at Albion Park at 10am, Nowra was hit by 100km/h winds while Bellambi Point recorded a gust of 98km/hr.

Mr Saunders said the gales are even stronger offshore and warned the swell will rapidly build along the NSW coast over the next 24 hours.

Swells of up to five and six metres are expected across the weekend.