The Bureau of Meteorology says snow falls have occurred right along the Great Dividing Range and as far north as Queensland's Granite Belt.
At its height, snowfalls of 15 centimetres and wind damage cut roads and rail access to the upper Blue Mountains for more than six hours.
In the Blue Mountains, 300 cars were stranded by the mountain road closures.
But the SES's Jennifer Finlay says most of the 550 calls for help came from further to the south.
"The Illawarra south coast got hit pretty hard with lots of trees down a bit of roof damage, fortunately nothing too severe," she said.
Endeavour Energy reconnected more than 2,000 properties to power on Friday afternoon, but hundreds of outlying properties between Mount Victoria and Medlow Bath and in the Megalong Valley will not get power back until Saturday.
With temperatures predicted to get down to 3 degrees Celsius overnight, the company has urged people in areas where the power is out to check on neighbours who live alone.