A smoke haze is hanging over parts of Sydney from a hazard reduction burn in the city's north, according to the New South Wales Rural Fire Service.
Crew are still working on the burn at Coba Creek, near Hornsby.
"We are experiencing a fairly significant smoke haze from the Hornsby hazard reduction," RFS spokesperson, James Morris said.
He added winds have pushed the haze through parts of the Northern Beaches, North Shore and CBD.
"That haze is expected potentially to settle over some of those areas overnight before clearing in the morning.
"It's expected to move in a northerly direction and then off the coast."
Sydneysiders took to social media to complain about the haze.
"So Sydney not only stinking hot but stinkin'," DeborahAnnG tweeted.
Nathan Dowd asked the RFS to "leave us asthmatics alone".
Others were concerned that there was a bushfire.
Mr Morris said areas north of Sydney up to Berowra would experience smoke in the morning before the haze was pushed offshore.
The RFS advised residents to make sure doors and windows were closed.
Those with respiratory issues were urged to seek medical advice.
