Strong winds across Australia's southeast coast today caused commuter chaos at Sydney and Melbourne airports, the country's two busiest, with thousands of air travellers stranded after dozens of flights were cancelled.

Winds gusting up to 70kmh also fanned major bushfires along the east coast, threatening homes and forcing evacuations.

Sydney Airport cancelled 76 flights after all but one runway was closed due to the strong winds, reducing flight movements to 23 per hour, more than half the usual rate.

"It’s not safe to have flights landing or departing and as a result we are going to a single runway, there are delays," Sydney Airport told Reuters.

Melbourne Airport also reduced the number of flights allowed to arrive and depart each hour due to Sydney Airport cancellations.

The strong winds fanned fires across New South Wales state, with Australia's Rural Fire Service reporting 21 fires.

A Boeing 737 modified for use as a waterbomber was used to fight bushfires around the city of Newcastle, north of Sydney, said the Rural Fire Service. The aircraft can carry 15,000 litres of water or fire retardant.

"(This) was the first operational drop that is done in the world... it has proven to be effective," Chris Garlick, a spokesman for the NSW Rural Fire Services told Reuters.

Fires around the popular tourist spot of Port Stephens, nearly 200km north of Sydney, forced an emergency evacuation of residents. There were no reports of injuries or loss of property. Emergency workers warned the strong winds threaten to escalate the fires.

The strong winds are part of a massive weather system over southeast Australia, that whipped up a 500km dust storm yesterday, which swept across the drought-parched interior to blanket Sydney.

The weather system also brought snow storms to southern parts of the country and around the national capital Canberra, due to icy winds and low temperatures in the southern end of the storm cell.

The Australian Bureau of Meteorology said winds would ease by today evening, offering some respite to travellers and fire fighters.

- Reuters