A rare and dirty wind storm that kicked up in South Australia and engulfed NSW on Wednesday may reach Brisbane and even New Zealand before the dust settles.

Winds up to 90km/h brought a thick orange hue to the skies over NSW as the dust storm moved east across the state.

Services to and from Sydney airport have been crippled and authorities have raised a health alarm for people suffering from chronic respiratory problems.

Strong westerly winds kicked up on this Tuesday afternoon and exacerbated drought conditions in far western NSW, whisking up dust and dirt from the already scorched earth.

"It (the dust) covers a big area of the state and certainly the eastern half of the state at the moment is under that," the Bureau of Meteorology's regional director Barry Hanstrum told AAP.

"And it looks as if it will continue to move up through the Northern Rivers area during today and maybe even make it into Brisbane at some time."

Mr Hanstrum said strong winds from South Australia sent dust across the Tasman earlier in September.

"And likewise with this one, there's a fair chance that it will keep going out into the Tasman Sea and it won't dissipate quickly," he said.

"They may see some effects of reduced visibility as far east as New Zealand."

The red dust storm now already engulfed southern Queensland, causing traffic delays, raising health concerns and cancelling horse racing.
Traffic has slowed on major routes across Brisbane, Ipswich and the Gold Coast.
Ipswich councillor Paul Tully described it as the worst dust storm in a decade.
Drivers in central Brisbane have begun to drive with lights on as the atmosphere in the city turns orange.
A Brisbane Airport spokeswoman said the airport remained open at noon AEST.
She said airport management expected a call from air traffic control on Wednesday afternoon that will close the airport when the dust thickens.

An intense low-pressure system formed over southern NSW on Tuesday and a band of gale force winds on its northern edge developed during the afternoon.

Mr Hanstrum said drought conditions across the state had intensified the rare weather event that has brought dust and reduced visibility to most of NSW.

"The winds whipped up a great dust cloud and that's been transferred across the whole of the state," he said.

Strong winds and dust hit Sydney at about 3.30am (AEST) on Wednesday, crippling Sydney airport and forcing international arrivals to divert to Brisbane and Melbourne.

Domestic flights continue to experience long delays, while ambulance and fire authorities have received far more than the usual number of calls.

The NSW Ambulance Service issued a warning to people suffering from asthma or other respiratory illnesses to stay inside where possible and carry all medication.

Police have urged motorists to slow down and put their lights on due to the extreme dust levels.

Mr Hanstrum said the winds had started to ease in western NSW and visibility had improved, with a similar easing of conditions expected to spread east on Wednesday afternoon and evening.

"We should see some sunshine again tomorrow (Thursday) although it will remain a bit hazy," he said.

Meanwhile, the NSW opposition pointed out that on Tuesday the Department of Environment and Climate Change's website forecast "good" air quality for Wednesday.

Opposition environment spokeswoman Catherine Cusack said the inadequate warning was a result of budget cuts.

"This ludicrous prediction that Sydney's air quality is good highlights to us how incompetent this government has become," she told reporters in Sydney.

"Our perception is that the entire air quality monitoring system in this state is defunct."

But Environment Minister John Robertson said the state's air monitoring system was the best in the country.

"The forecast weather conditions prior to the dust storms included rain, resulting in there being no prediction of high pollution," Mr Robertson told parliament.

"However, as soon as air quality exceedences began to be recorded ... health alerts were automatically generated."

The director of NSW Health's Environmental Health branch, Wayne Smith, said it would not have been possible to predict the high levels of pollution.

"The warnings were up early this morning," Dr Smith said.

"It would be nice if these forecasts could happen a bit earlier, but there is usually not good warning for these events.

"It's inappropriate to be putting out warnings when we don't know the warnings are going to be needed."

Also on Tuesday, the dust brought construction work across the city to a halt.

The Construction, Forestry, Mining and Energy Union (CFMEU) has closed all major building sites because workers are experiencing eye irritations and respiratory problems.

CFMEU assistant secretary Brian Parker said one worker had collapsed on a work site in Newtown due to respiratory problems.

© AAP 2009