The fire danger in New South Wales will peak within hours as firefighters battle more than 30 blazes across the state with some rural properties under threat.

Watch-and-act alerts were issued for bushfires at Warrabah near Tamworth and Tingha Plateau in the state’s north-east with Fire and Rescue NSW warning fire activity was increasing in the area.

High temperatures and strong winds were fanning the out-of-control Linton fire with a number of rural properties under threat.

The fire at Tingha Plateau had burnt more than 300 hectares and was also not under control, the Rural Fire Service said in a statement on Tuesday afternoon.

Crews were battling 33 bush and grass fires across the state with nine not yet contained.

A statewide fire ban was issued for Tuesday with temperatures tipped to reach the low-40s in some areas accompanied by high winds.

The Bureau of Meteorology issued a fire weather warning for much of the state, with the fire danger to peak on Tuesday afternoon.

The Hunter Valley and surrounds faced extreme fire danger while the rest of NSW was under severe to high fire danger warnings.

Strong winds, warm low-level temperatures and dry conditions combined with dry fuel from heatwave conditions in past months had led to an elevated fire danger, a BoM spokesman said.

The fire danger was set to peak as maximum temperatures were recorded in the afternoon, the spokesman said.

But a southerly change was expected to move through from the state’s south later, hitting Sydney in the early hours of Wednesday.