A polar air mass moving up the country is forecast to bring cold temperatures and snow across the South Island, while heavy rain and wind stick around for the North Island.

MetService meteorologist Josh Griffin said there had been an active rain trough moving across the top of the North Island this weekend and was expected to spread across the top of the South Island today.

“In conjunction with that, starting tonight, we’re going to have a cold front moving onto the far south of the South Island which will be spreading northwards today,” he said.

“As that cold front moves northward it will meet with the warm northwesterly air moving down.”

Pedestrians in Central Auckland run across the road to avoid the rain. Photo / Sylvie Whinray

Griffin said there would be snow risks for parts of the South Island today, in places such as inland parts of Canterbury up to places like Waipara.

“We’re looking at the heavier falls forming about 500 metres or so but there could be some snow falling at lower levels down to about 200 metres.”

A heavy snow watch is forecast to come into place from 1pm until 10pm for inland parts of Canterbury.

Road snowfall warnings are set to start for Crown Range Rd, Porters Pass, Arthurs Pass and Lewis Pass from late this morning until 10pm.

Between 3-12cm of snow is expected to accumulate on the roads above 800 metres.

Griffin said the heavy rain would continue for Auckland today with the potential for squally thunderstorms.

“We are also going to potentially see some strong wind gusts with some of the heavier showers and thunderstorms,” he said.

“But heading into Monday, it looks like it will be rainy before dawn but ease off during the day.”

Weather heading for snow in Lake Tekapo in the South Island. Photo / Hayden Woodward

Heading to Monday, Griffin said there would be another cold westerly flow heading onto the South Island.

“In places like Central Otago, Southland, Clutha and Fiordland, there will be frequent showers and some of the showers could have the potential to generate heavy snow around 400 metres,” he said.

“Temperatures were forecast to reach single digits in places such as Invercargill and Southland.

“The warm moist air that brought heavy rain to the top of the North Island came from the tropics while the cold fronts came directly from Antarctica.”