An outback dust storm swept across eastern Australia and blanketed Sydney on Wednesday, disrupting transport and placing health authorities on alert for widespread respiratory illness.
The dust blacked out the outback mining town of Broken Hill on Tuesday, forcing one mine to shut down, and then swept east, shrouding Sydney in a red glow on Wednesday morning.
International flights were diverted from Sydney, ferries on Sydney Harbour were suspended and commuter motorists warned to take care on roads as visibility was dramatically reduced.
Health authorities urged people with asthma or breathing difficulties to stay indoors. The dust set off smoke alarms in some buildings in Sydney's central business district.
"People at risk are children, elderly, pregnant women, people with heart and lung diseases. Dust particles can increase the risk of people with these conditions becoming unwell," said Wayne Smith from the New South Wales state health department.
The Bureau of Meteorology (BOM) said a major cold front in New South Wales state caused severe thunderstorms and gale-force winds, which whipped up the dust from the drought-stricken inland and spread it across Australia's most populous state. The 100 kilometer per hour plus winds also fanned bushfires in the state.
"This is unprecedented. We are seeing earth, wind and fire together," said Dick Whitaker from The Weather Channel.
Australia is the driest inhabited continent on earth, and the NSW state government recently cut the state's 2009/10 wheat crop estimate by 20 percent because of hot, dry weather across the grain belt.
The country is one of the most vulnerable nations to climate change, but also the world's biggest greenhouse gas emitter per capita as it relies on coal-fired power stations for the bulk of its electricity.
Sydney residents told local radio that they woke to scenes from a Hollywood disaster movie, while many contacted emergency services fearing a major bushfire in the city.
Karen from Sydney's inner western suburb of Dulwich Hill said she woke up to find the red dust had covered her floors and birds had been blown out of their nests.
"It did feel like Armageddon because when I was in the kitchen looking out the skylight, there was this red, red glow coming through," Karen told Australian Broadcasting Corp. radio.
The blanket of dust stretched hundreds of kilometers along the coast from Sydney, from the coal port of Newcastle in the north to the steel city of Wollongong in the south, and hundreds of kilometers inland to farming towns like Dubbo and Tamworth.
"In the south, where there are showers, people will find it is falling as mud this morning, but that will help clear the dust from the air," said the BOM spokeswoman.
Steve, who was driving to Tamworth in the northwest, told local radio: "It's almost raining mud. I have a green car and it's now an orange car. The wipers are barely able to cope with all the mud."
Weather officials said the blanket of dust would remain for several hours, until winds eased.
Further cold fronts are expected later in the week and could bring not only more strong winds, with the chance of dust storms, but also snow falls on Australia's alpine region, said weather officials.