Fire crews are hoping a cool change overnight will help them gain the upper hand on an out of control fire which has already destroyed two properties in northern New South Wales.

More than 100 people are sheltering in evacuation centres after the blaze burning in the Warrumbungle National Park threatened communities near Coonabarabran and forced the evacuation of at least one town.

Authorities also say thousands are without power across the state's north after storms overnight.

Large parts of the state have been impacted by bushfires this week, brought on by searing temperatures and wild winds.

Firefighters are also working to control blazes in and , while the .

A spokeswoman for the Rural Fire Service says they are now confident of protecting the town of Bugaldie, after an emergency warning was issued and the town was evacuated overnight.

Residents north of Bugaldie had been advised to evacuate to Baradine if the path was clear and those south of Yearinan were told to head towards Coonabarabran.

About 112 people are now sheltering at the evacuation centre at the Tattersalls Hotel in Baradine and more have spent the night at the Coonabarabran Bowling Club evacuation centre.

RFS superintendent Matt Inwood says cooler conditions overnight may allow fire crews to gain the upper hand.

"Fire fighters will have a good opportunity to try and get some good containment lines in around that fire," he said.

"At this stage it's been a complete effort on concentrating on property protection and ensuring the safety of all residents and firefighting crew in that area."

The RFS says more crews will arrive in the area at first light to help battle the 1,000 hectare blaze.

On Sunday evening the bushfire destroyed two properties on Timor Road, near Coonabarabran, and damaged the major Siding Spring Observatory.

The RFS says all staff were evacuated before the fire hit and the main telescope at the observatory has survived.

Authorities have downgraded the alert for a bushfire near Bundabarina to watch and act, after the blaze earlier jumped containment lines and threatened the town of Collarenabri.

Around 40 fires were sparked by lightning across a large area in the north on Saturday night, with temperatures above 40 degrees hampering efforts to bring them under control.

Crews are now fighting more than 130 fires across the state, of which 30 are uncontained.

The RFS has now moved resources to the state's north in response the new fires.

Southern fires contained

Meanwhile, cooler conditions on Saturday evening helped crews strengthen containment lines around two large bushfires in the state's south.

A large blaze near Yass has been contained in rugged country, but fire crews are strengthening containment lines to prevent flare ups.

Southerly winds are also pushing smoke over the town of Bookham, while access to Burrinjuck Dam has reopened.

The cool change has also provided welcome relief for fire fighters battling the Yarrabin Fire near Cooma.

It is currently west of Tuross Road in the Kybeyan area and is not threatening properties.

Fire crews are also working to gain control of a large blaze at Sussex Inlet in the Shoalhaven.