Traffic has queued for almost 10 kilometres after a grassfire crossed over the top of motorists on the Hume Highway in NSW and led to a road closure.
The blaze near Wingello, midway between Sydney and Canberra, was the most serious of about 90 fires to break out across NSW on Saturday as the mercury reached 40C in some areas.
The main arterial road between Sydney, Canberra and Melbourne was closed for about five hours before it was reopened about 6pm.
Northbound traffic was banked back seven kilometres while southbound vehicles were queued for 2.5 kilometres, the NSW Transport Management Centre said.
A large air tanker was used as Rural Fire Service crews fought to control the small but ferocious blaze.
"It was quite scary for motorists when it did jump the road because reports are the fire went right over those cars," Deputy Commissioner Rob Rogers told the ABC.
"We don't want a repeat of that again."
Firefighters have begun backburning to contain the fire and have warned drivers to proceed with caution due to smoke and people remaining near the highway.
While scores of fires ignited elsewhere on Saturday, none reached the watch and act level.
The RFS forecasts another difficult day on Sunday with much of the state's northeast considered to be in severe danger of fire.
The Greater Sydney region is among eight areas that will be under a total fire ban.
Newcastle, Tamworth and Gunnedah are among the centres expected to endure temperatures in the mid-30s and windy conditions.
