The exceptionally dry conditions around Sydney and much of the state have prompted the Rural Fire Service to scale back hazard reduction burning this weekend.

A burn planned for about 100 hectares in the northern beaches has been delayed indefinitely, while other fires are being reviewed, Ben Shepherd, head of RFS media, said.

Two small burns, one near Mona Vale Road and another in The Hills region, will proceed on Sunday, weather permitting.

As of Friday afternoon, about 60 fires were burning across the state, with 25 uncontained, Inspector Shepherd said.