Canobolas Zone NSW RFS is reporting an easterly influence overnight again brought smoke in from fires out of the area.

The biggest fire east of Orange remains the Gospers Mountain blaze in the Wollemi National Park at Hawkesbury.

The alert level on that fire is watch and act with the fire's status as 'being controlled', but the 303,122 hectares burnt out is a substantial area.

Canobolas Zone says the haze across Orange on Sunday morning should clear late in the afternoon, but return again in the morning.

The smoke blanket will serve as a summer precursor to a potentially record breaking run of extremely hot days in the city.

The mercury is set to hit 33 degrees Celcius on Monday before reaching 36 on Tuesday. The hottest recorded December day in Orange is 34.7 degrees in 2009.

Wednesday and Thursday will both be in the 30s as well, 34 and 30 respectively, before a coolish change returns Orange's top temperatures back to the mid-20s as the weekend approaches.

Orange's expected recorded-breaking temperatures come on the back of extreme heat conditions across Australia, with Brisbane recording the warmest pair of days this early in summer in over 51 years, with the mercury peaking at 37.7 and 38.6 last Thursday and Friday respectively.

A total fire ban remains in place for the Central Rangers.