Unseasonable snow fell in the town of Katoomba about 120 kilometres (74 miles) west of Sydney on Friday (October 12).
Kangaroos normally expecting to enjoy spring sunshine were left hopping around in snow right in the town centre.
Up to 300 motorists were stranded in their vehicles as roads were closed, Network Ten reported.
Trains stopped running in the area because of snow covering the tracks.
Residents said they were surprised by the snowfall.
"It's October for heaven's sake, we should be swimming not building snowmen," said one unidentified Katoomba resident.
Temperatures fell to below zero degrees celsius in the Blue Mountains, the Bureau of Meteorology reported.
