"In Queenstown tomorrow night - they drop down to freezing. They could see some snow on the higher grounds across parts of Otago, Southland."
Mr Corbett said a band of rain is moving up the South Island, bringing heavy rain to the West Coast this morning.
The system is also bringing rain to the east of the alps and will move up the country in the coming days.
Fortunately the cool weather will not be sticking around long, moving through each area in around 6 to 10 hours.
"The active weather system will bring a bout of heavy rain in places, along with the risk of some thunderstorms over northwestern areas of the North Island. This weather system will depart the North Island on Thursday and will be followed by a noticeably cooler southwest change
"The cooler air that will spread over New Zealand in the wake of this weather system will certainly have a taste of Autumn."
Mr Corbett said the air will start to warm ahead of the weekend, as a large anticyclone builds to bring dry and settled weather.
"There's a nice ridge of high pressure over southeast Australia and it's setting its sights on New Zealand for the coming weekend. So after we've got this wet weather and a little bit of a cool-down over the South Island, we've got a nice high to look forward to this weekend."
- HERALD ONLINE