The Great Western Highway is closed in both directions near Jenolan Caves Road at Hartley, while snow is also impacting highway traffic near Katoomba.

A truck breakdown at Mount Victoria is also creating a hazard for motorists travelling between Bathurst and Lithgow.

Oberon Council has also advised of a number of road closures following overnight falls.

"With snow in and around Oberon the O'Connell, Duckmaloi, and Abercrombie Roads are currently closed," the council posted on its website.

"Roads are being inspected and we will update as information comes to hand.

"Please drive to conditions as some smaller roads may also be affected by snow."

VIDEO: Snowing in Oberon at 5.30am ...

Meanwhile, NSW Police have also urged caution on the roads.

Traffic and Highway Patrol Assistant Commissioner Michael Corboy said unpredictable weather conditions across the state meant an increased risk of drivers and riders being involved in crashes.

"There are several parts to these warnings, some or all of which may come into play in the coming days," Assistant Commissioner Corboy said.

"Firstly, it hasn't rained for some time so the roads will be covered in grime which will become slippery to drivers as well as bicyclists and pedestrians.

"Visibility is important - that means headlights on and if you are on foot or a bike of any kind - this is the week for your brightest coat and/or umbrella.

"Later as the rain continues, we will see water running over the road and pools of water forming. Drivers can easily lose control.

"Days of rain can often result in road closures. When that happens, people may be tempted to ignore road closed signs and drive through flood waters.

"It's not just your life at risk - it's the lives of the emergency service workers some of whom are volunteers."