Two locations in western NSW appear to have just broken Australia's high minimum temperature record.

The lowest temperature observed at Noona and Borrona Downs and during the 24 hours to 9am on Friday January 18th were 35.9 degrees and 35.6 degrees respectively.

These 'low' overnight temperatures beat Australia's previous high minimum temperature record of 35.5 degrees, which occurred in WA's Wittenoom in 2003 and SA's Arkaroola in 1982.

Earlier this week, Borrona Downs registered the highest minimum temperature on record in NSW with a low of 34.6 degrees on Monday morning.

This morning's unprecedented minimum temperatures occurred amid an extreme heatwave that has broken a plethora of heat-related records in a number of states and territories this week.

This heatwave will target much of NSW, the ACT and parts of central Australia today, with temperature likely to reach the mid-forties in many areas.

It's difficult to compare Australia's new minimum temperature record with the rest of the world. Unfortunately, the World Meteorological Organisation's Climate and Weather Extremes archive does not include information the highest minimum or lowest maximum temperatures.

In June last year, a weather station in the coastal town of Qurayyat, located to the east of Oman's capital city Muscat, registered a minimum temperature of 42.6 degrees Celsius. Some weather experts suggest that this could have been the highest 24-hour minimum temperature on record anywhere in the world.