Highways reopen after NSW fire risks

Major roads connecting greater Sydney to the rest of NSW are flowing again after catastrophic bushfire danger prompted their closure.

Transport for NSW on Saturday evening reopened the Hume Motorway between Sutton Forest and Narellan, as well as the Picton Road at the M1 and the Princes Highway between Falls Creek and north of Milton.

In the Blue Mountains, the Great Western Highway earlier reopened in both directions between Katoomba and Lithgow but the Bells Line of Road and Chifley Road are closed between Kurrajong and Lithgow.

Stretches of Megalong Road, Jenolan Caves Road, the Castlereagh Highway and Bowen Mountain Road remain shut.

Train lines between Campbelltown and Moss Vale, to the south, and westwards between Katoomba and Bathurst have also been impacted.

NSW Police assistant commissioner Karen Webb said earlier on Saturday the state's residents should delay all non-essential travel.

"Delay your travel until tomorrow ... conditions will be much milder and you can have a better trip," Ms Webb told reporters.

Ms Webb later said commuters and travellers were "getting the message" to undertake essential travel only.

Fire danger was rated "catastrophic" on Saturday in the Greater Sydney, Illawarra-Shoalhaven and Southern Ranges regions and "extreme" in the Hunter, the ACT and the Central Ranges.