Smoke from more than 50 fires burning in northern NSW has covered Sydney with clouds of smoke even reaching as far away as New Zealand.
NSW Health warned people in Sydney and the Hunter to take precautions with smoke blowing south from fires on the state's mid-north coast causing poor air quality from Monday afternoon.
The air quality reading for Sydney on Tuesday morning was 122, a level considered unhealthy for sensitive groups.
In Newcastle, the level, which measures microscopic particulants that can be breathed in, has reached 164 which is unhealthy for anyone.
People with existing lung and heart conditions like asthma, emphysema and angina are advised to stay inside with the doors and windows shut.
Satellite images have shown the extent of the spread of the smoke and dust with New Caledonia and southern Vanuatu expected to be impacted.
with high temperatures, low humidity and strong winds forecast.
With more than 50 fires burning across the state, the NSW Rural Fire Service has warned people that leaving early is the safest option.
The smoke may cause mild symptoms like sore eyes, nose and throat.
But most city residents posting photos of the haze were far more concerned for those under threat in regional and rural areas and firefighters trying to protect communities.
JC tweeted the haze over Sydney was "incredible and unnerving".
"Sending thoughts to everyone dealing i nthe fire affected areas, stay safe."
