Total fire ban issued during NSW heatwave

A total fire ban has been issued for the NSW Southern Riverina as the state swelters through a four-day heatwave.

The area has been given a severe fire danger rating for Wednesday, with high and very high ratings in place across the rest of NSW, not including the Far North Coast.

NSW Rural Fire Service spokesman Paul Best says crews are on standby with high temperatures and low humidities forecast in the region along the NSW-Victoria border.

"There are wind gusts in that area of 60km/h, so if a fire was to start you would expect that it would be a fairly fast-moving fire," he told AAP.

The RFS is also issuing a reminder for residents to have a bushfire survival plan.

"If they haven't made a plan, they still have tonight to sit down and work out what they should do," Mr Best said.

He said crews sent to assist Tasmania have not depleted resources to fight fires in NSW.

Temperatures are expected to hit 32C and 34C in central Sydney over the next two days, 39C and 41C in Penrith, and 40C or more across rural NSW.