"That cold southerly will bring snow to about 100m in the far south tonight," Moes said.
Standard July temperatures are in store for most of the South Island, but Invercargill will have a high of 6C and a low of -4C, which Moes said is below average for this time of year and has been caused by cold southerly winds.
A heavy snow warning is in place for inland parts of Canterbury south of Fairlie and the Mackenzie Basin, although most of the snow fell yesterday.
"That's for heavy snow above 400m and that should ease this morning, we're just on the tail end of that now," Moes said.
There will be heavy snow about eastern parts of the South Island until Saturday.
A severe weather watch is in place for snow above 400m in Canterbury and the Kaikoura Coast and ranges, Dunedin and South Otago for tomorrow and Saturday.
As the frosty temperatures bring with them a chance of snow, WeatherWatch has a service which allows you to find out if it will snow where you are.
All you need to do is type in your location and it will tell you if snow is in the forecast, the percentage of precipitation and 10 days of overnight lows and daytime highs.
According to WeatherWatch, snowfall over the incoming polar blast will only be heavy above 100m to 200m in the south and 300m to 400m in the north.
In the South Island wind chills will be anywhere from -5C to -15C in some exposed farming and growing communities. Overnight lows in inland South Island areas like Alexandra will drop below -10 in calm conditions.
According to WeatherWatch a cold Antarctic airflow that's hitting a low over the North Island is the cause of the frigid temperatures, with the heaviest snow occuring when cold Antarctic air hits warmer moist air.
While most of the heavy snow has subsided for much of the South Island, chilly temperatures are looking to set in for the weekend.
There will be a persistent south easterly flow over the South Island, Metservice meteorologist Angus Hines said.
For Christchurch the average minimum temperature will be -2C and the maximum will be 7C.
Dunedin's maximum temperature will be 6C. A severe weather warning has been issued by Metservice for a heavy dump of snow in Canterbury overnight tonight and tomorrow.
Snow of 20cm could accumulate 400 metres above sea level.
Weather Watch head analyst Philip Duncan said flights may be affected by the wintry conditions across the country over the next few days. However the conditions didn't look too extreme, he said.
The wintry outbreak brought a mix of snow, gales and severe ice to some airports
He advised travellers to regularly check forecasts and airports before travelling.
• Queenstown Airport
Not a huge amount of snow, but plenty of ice with overnight lows down to -10C likely at the airport over the weekend there might be delays due to de-icing both planes and the runway.
• Dunedin Airport
Snow showers off and on across Thursday and Friday but hopefully not enough to cause serious problems.
• Timaru Airport
A few snow showers on Friday, generally not too heavy but might cause possible delays with smaller aircraft until conditions clear. Some risk for delays.
• Christchurch Airport
A little bit of snow possible on Friday but at this stage doesn't look too problematic. One to keep an eye on though.
• Wellington Airport
Snow is above 300m so that's well above the airport, but the gale force south easterly winds could cause a few delays, mainly with smaller aircraft on Friday night or Saturday.
