Weather: Freezing start the day, temperatures plummet to -7C in the south

New Zealanders have had a freezing start to the day with with temperatures in parts of the South Island plunging to -7C, and bitter frosts in many places.

Metservice Meteorologist Devlin Lynden in the north, Taupo hit a chilly -5.1C in the morning, and cold temperatures had spanned across the North Island.

In the South Island, the Mount Cook / Pukaki area registered a freezing -7C .

Shortly after 7am Twizel was still shivering at -7.5C, the MetService site recorded.

It followed a weekend of torrential rain and cold weather for many, with thunderstorms in Wellington and a "river" of water on the city's Tinakori Road.

MetService recorded the lowest temperature on Sunday at Mt Cook where the mercury plunged to -6.3C in the morning.

Lynden said the cold weather was set to continue through to at least Wednesday, particularly in the North Island, with a ridge of high pressure over the country.

"That means that overnight, that heat that we get from the sun through the day really escapes, and those temperatures plummet," he said.

"That, combined with really light winds, means that particularly in those sheltered valleys, we can see temperatures drop quite considerably."

Around Wednesday Lynden said northerly winds would pick up for the South Island first, bringing temperatures up a tad.

"Then through into Thursday, a more northerly trend picks up for the whole country and temperatures will continue to climb," he said.