As a haze hung over Sydney on Saturday, residents in parts of the city were warned to avoid outdoor activities as the air quality reached "hazardous" levels.

High pollution levels were recorded across the Sydney basin on Saturday, as hazard-reduction burning efforts are stepped up ahead of an expected active fire season.

Bases loaded: hazard-reduction burning along Wakehurst Parkway in Sydney's Northern Beaches on Saturday. Credit:James Brickwood

Sunday will see a spike in temperatures and a pickup in winds, with little sign of rain for at least a week.

Rural Fire Service Deputy Commissioner Rob Rogers said he hadn't seen conditions this dry so early in the season for 10-15 years.