An out-of-control grassfire passed over the top of motorists on the Hume Highway shortly before traffic was closed in both directions.
The blaze near Wingello, midway between Sydney and Canberra, is one of more than a dozen fires yet to be contained across NSW.
An emergency warning issued to residents and drivers near Wingello was downgraded about 3.40pm on Saturday afternoon.
The Hume Highway remains closed in both directions after the fire crossed the main arterial between Melbourne, Canberra and Sydney.
Traffic won't be allowed through again until the Rural Fire Service "can be convinced it will be safe" to do so.
"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."
Residents in the area of Hanging Rock Road and southbound drivers were advised to drive towards Sydney.
"We're aware it is disrupting a lot of people who want to get away for the weekend and the school holidays," Mr Rogers said.
Fires are also out of control near Tenterfield in the state's north.
A severe or very high fire danger rating was issued for Saturday as the mercury reached 33C in Sydney and cracked 40C in the far north-western town of Bourke.
Further fires are expected on Sunday with much of the state's northeast considered to be in severe danger of fire.
The Greater Sydney region is among eight fire areas that will be under a total fire ban.