Houses under threat from out-of-control bushfire in the Hunter Valley

A fire broke out near Cessnock in the NSW Hunter Valley region. Houses are under threat from an out-of-control bushfire. Photo / AAP

Houses are under threat from an out-of-control bushfire in the New South Wales Hunter Valley with the Rural Fire Service issuing an emergency warning.

The RFS issued the warning for Richmond Vale, outside Cessnock, today.

The fire has broken containment lines and a number of properties are under threat - so far 381ha of bushland have been burned, the RFS website states.

Waterbombing aircraft and two helicopters are working with 14 firetrucks and 45 firefighters to contain the blaze, an RFS spokesman told AAP.

Residents of the rural community of Stanford Merthyr have been told if they plan to evacuate they should do so immediately.

In Sydney, RFS units are working to bring a fire in Sydney's north back under control. The Beacon Hill blaze, which began yesterday, was contained by more than 100 firefighters but flared up again today.

The fire was at Watch and Act threat level with no properties under threat but smoke blanketing the area.

Total fire bans have been declared across swathes of the state, prompted by hot and windy conditions. The RFS declared four regions as having a severe fire danger including Greater Sydney Region, Greater Hunter, North Coast and North Western regions.

Temperatures in the mid-30s and strong north-westerly winds are creating challenging conditions for firefighters. Winds are forecast to reach 40-50km/h with gusts up to 70km/h.

- AAP