Maitland and Cessnock are expected to swelter in 40-plus degree heat on Wednesday and Friday as a run of hot days this week reaches its peak.
Lower Hunter residents tried to keep their cool on Monday and Tuesday as temperatures reached the mid to high 30s.
The mercury reached 36 degrees in Maitland at 2pm on Monday while Cessnock recorded 37.1 degrees at 2.30pm.
Forecasters have warned that the situation is likely to get worse for inland parts of the Lower Hunter in the second half of this week, with tops of 41 degrees expected for Maitland and Cessnock on Wednesday and Friday.
A brief cool change is forecast for Thursday, with 28 expected in the valley.
The heat will be much less severe on the coast, with Newcastle tipped to reach 34 degrees on Wednesday and 30 degrees on Friday.
According to Weather Zone, a cool change in eastern NSW on Sunday will be short-lived, with warm northerly winds expected to bring more heat next week.