Blazes at Mount Kingiman and North Nowra, which threatened homes on Wednesday, have been downgraded amid cooler and calmer conditions but hundreds of firefighters remain on scene.

"Although there's no threat to properties, we do have fire crews working with local residents and landowners to deal with the fires as they approach," NSW Rural Fire Service spokesman Chris Garlick told AAP.

A total fire ban was issued for Sydney, the Illawarra and Hunter regions on Wednesday - something not seen so early in the season in nearly a decade.

NSW RFS Commissioner Shane Fitzsimmons said the drought was having an enormous impact.

"In my time I don't recall quite as many fires and the length and breadth of the fires," he said. "It's shaping up to be a long fire season if we don't get any drought-breaking rain."

The Princes Highway has reopened in both directions between Cambewarra Road and Bolong Road.

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In times of fire danger, follow your Bush Fire Survival Plan. If you do not have a Bush Fire Survival Plan, ensure you know what you will do if the fire threatens your property.

If you are in doubt or it is not safe to leave, take shelter in a solid structure when the fire front arrives. Protect yourself from the heat of the fire. If you are caught in the path of the fire, you may die or be injured.

- By Robert Crawford, Rebecca Fist, Emily Barton, Sam Strong, Damian McGill, Hayley Warden, Courtney Ward, John Hanscombe