The state record for the hottest day in September has been broken for the second time in a week in parts of western New South Wales.

In the upper west, Delta has hit 41.3 degrees Celsius and in Bourke it reached 40.7C.

Loading

Other towns which are also expected to reach 41C include Tibooburra, Bourke, Lightning Ridge, Walgett and Mungindi.

The latest record was only just set on Saturday when the town of Wilcannia reached 40.5C during an unseasonal heatwave.

Prior to that, the last record was set on September 28, 2004 with the temperature hit 39.6C at Wanaaring.

Bureau of Meteorology forecaster Andrew Haigh said the new record was extraordinary for this time of year.

"It's very unusual, evidenced by the fact that we are breaking all time September records in NSW in terms of highest temperatures, so in that sense very unusual," Mr Haigh said.

Children on school holidays in Bourke tried to beat the record heat with a dip in the local pool ( Supplied: Bourke War Memorial Olympic Pool Complex )

A total fire ban has been issued for the entire far west region of the state.

Rural Fire Service district manager from the far west, Vaughn Elsworth, said it was mainly the winds that made the hot temperatures concerning.

"I mean we had a hot day on Saturday across the same area, but ... I guess the risk for us is the severe winds that come with those high temperatures," Mr Elsworth said.

"I guess one of the saving graces we do have, talking to some of the farmers, is the fuel load on the ground is not as severe and while we will get pockets of fire, we're not going to potentially see large areas affected."

The small town of White Cliffs is experiencing 78 kilometre per hour winds.