Strong winds have created a dusty haze over St George and Sutherland Shire and much of Sydney reducing the air quality to hazardous in some areas.
Weatherzone warned the air quality may deteriorate in some areas before it improves when a change moves through later on Wednesday.
Weatherzone meteorologist Graeme Brittain said hot, dry, gusty north-westerly winds on Tuesday have brought the dust to the coast.
The airborne dirt tracked through the Riverina earlier on Tuesday and moved across Canberra on Tuesday afternoon.
"It picked up the dust lying on the ground and then has vectored it - moved it - south-eastwards across NSW so it has arrived over Sydney over the last several hours," he said.
Mr Brittain said the dust, was also affecting air quality across the state.
"We could expect a deterioration in Sydney's east in the next few hours before it improves," he said.
The meteorologist said the dust is expected to hang over the city for most of the morning, but conditions are forecast to improve later in the day as the strong cold front moving across the south-east of Australia moves further north and east.
The dust storm was being created as blustery north-westerly winds picked up dry top soil across drought-stricken areas of western and southern inland NSW.
It is the latest in a series of dust storms that have affected NSW after a prolonged run of drier than usual weather throughout most of last year.
