Snow was forecast to fall about 100m above sea level in Dunedin, Invercargill and Christchurch but Dunedin has already seen snow reach sea level.
Ice and snow are causing major disruptions to many Dunedin bus services. The Otago Regional Council says the hill suburbs are worst affected.
In Christchurch, emergency services reported snow flurries this morning. But the white stuff was likely to stick mostly to the hills, Adams said.
"Will it snow on the beach? I doubt it. Will it snow in the hills? Quite likely."
Invercargill Z petrol station worker Tawhiri McPherson said snow hadn't fallen in the city, but he understood one of their stations in Balclutha may have to close today because of snow.
MetService meteorologist Tom Adams said some farmers in the deep south have reported a few centimetres of snow falling in the South Otago settlement of Clinton and at Jollies Pass in Lumsden.
The heaviest bands of rain, which fall as snow on higher ground, have already been through, but showers remain on the horizon.
"If you haven't had snow yet, it doesn't mean you are not going to get it," Adams said.
Despite the excitement, the weather was fairly standard for this time of year, he said.
"It certainly shouldn't happen every day, but we'd expect to get two or three of these events each winter."
A significant amount of snow is expected to fall across the Central Plateau, Hawke's Bay ranges and Wellington region as the cold air invades the North Island.