Sydney Harbour Bridge just after 7.30am, obscured by smoke.(Nine)
Much of southern NSW is waking up to a blanket of smoke this morning following hazard reduction burns over the weekend.
Fog is also having an impact across Sydney , with forecasters saying it will last into the morning and warning commuters to take care.
Sydney Harbour Bridge was gradually obscured as smoke moved in between 7am and 7.30am.
Multiple ferries have been cancelled.
Services on the Parramatta River, Pyrmont Bay and Cockatoo Island routes won't run and Sydney Ferries doesn't know when they will restart.
The NSW RFS is warning smoke is likely to settle on the Central Coast, and in the Blue Mountains, Snowy Valleys, Southern Highlands and the Illawarra and Shoalhaven.
Health Minister Brad Hazzard warned people with asthma to be "very cautious."
"It can certainly affect your lungs as it is me at the moment," he told Today.
"Stay inside if you can and make sure you use your preventers."
Air quality in parts of Sydney is at very poor levels, according to Air Quality Concentration Data, with Chullora, Earlwood, Lidcombe and Liverpool the worst affected.
Light winds have made the smoke settle in residential areas, the RFS is warning, but they said it will lift as the day goes on.
"Strategies have been put in place to reduce the impact of smoke on the community, including the postponement of a number of planned burns and a reduction in area burnt for others," the RFS said in a statement.
"Hazard reduction burning is strategically planned to minimise the potential impact of smoke on public health however, some members of the community may need to take action to mitigate the risks of smoke from hazard reduction burning by planning ahead."
Australia weather forecast
Sydney will be a sunny 26C.
Canberra is also foggy, with showers increasing and a maximum temperature of 21C.
Melbourne is wet and 19C.
Brisbane is a warm 25C, but showers are expected. Rain is also on the way in Adelaide, were it will be 20C.
Perth will be a mainly sunny 26C. Cairns is 29C but will remain cloudy.