Furnace-like conditions will sweep across large area of NSW and the ACT at the end of this week as a goodbye to spring.
The Bureau of Meteorology said heatwave conditions were expected to reach the Severe category in many locations
BOM forecast both daytime and overnight temperatures would be 10 to 16 degrees C above average for this time of the year, reaching into the high-30s or mid-40s during the day for many locations, from Thursday.
Conditions were also likely to see the fire risk increase significantly over the weekend.
Ben Domensino, from Weatherzone, said a mass of hot air from central Australia would drift across NSW during the next few days ahead of an approaching low pressure trough.
While hot weather was normal for NSW at this time of year, this week's heat would be more intense than usual for late spring, he said.
This was partially due to a lack of cloud cover over northern Australia in recent weeks which allowed hot air to build up over the nation's tropics and interior.
Daytime temperatures would be around 10 to 15 degrees above average on multiple days in some areas of western NSW, he said.
West of the Dividing Range temperatures would become oppressive in many areas, Mr Domensino said.
Temperatures would reach the low-to-mid forties somewhere in western NSW each day between Friday and next Tuesday.
Cobar should reach around 45 degrees C on Sunday which would not be far off its springtime record of 45.7 degrees from November in 2014.
Moree could also nudge 45C during this heatwave which could beat its spring record of 44.7 degrees from November 1944.
The highest temperature ever reliably recorded at an official NSW weather station during spring was 46.8 degrees at Wanaaring in November 2009.
