Several hazard reduction burns have seem the smoke engulf the city, with dramatic footage showing how it has settled.
Poor air quality is expected across the city today.
The hardest hit areas include Sydney’s north-west, Parramatta and other regions in the west, where levels are deemed “unhealthy”.
Fires are currently burning at the Royal National Park and Ku-Ring-Gai National Park.
The RFS warned favourable conditions would mean multiple burns would be going on this weekend and would create lingering smoke.