A bushfire here in northern Sydney, near Lane Cove National Park, is threatening a number of homes.

Firefighters are working to contain the blaze as smoke from the flames forces the closure of major motorways - causing widespread traffic problems.

Local media said the fire service believe the blaze was sparked by arson.

Meanwhile the southern state of Victoria has been hit with a snow storm on the fifth day of summer.

Local reports said that temperatures dropped to 1.7 degrees Celcius, and that about six centimetres of snow had already fallen.