Weather: Wintry school holidays forecast with cold snaps and snow

It might officially be spring, but these school holidays will feel like an extension of winter with chilly cold snaps and snow to blanket parts of the country, according to NIWA forecaster Chris Brandolino.

After a toasty weekend in many places, this week will be a reversal of fortunes for those looking forward to summer, with weather forecast that is normally found in July - not September or October.

"It won't be a bad week, if it were mid-July," Brandolino told The AM Show.

"We have had some pretty warm temperatures yesterday. Third-warmest September temperature in Christchurch on record for the city. 25.8C, so it was warm.

"This is ahead of a southerly change that will be working its way over the next 24 hours or so through the country."

Brandolino said it's going to be a very "active morning" for the North Island, with rain and gusty thunderstorms before that cold change makes it way up from the South Island on Monday night.

"The cold starts moving north tonight over the lower South Island. Snow levels will lower," he said.

"If you have, maybe, a late-season ski holiday planned for school holidays, you are probably going to do better than you'd maybe in June or July."

Asked by The AM Show host Duncan Garner if this week could be considered a "winter extension", Brandolino agreed.

He said even after the southerly change comes along, cold snaps will continue to hit the country in the weekend - potentially dangerous for lambs.

"Later in the week, the cold will be here, but the unsettledness will go, so if you time that right, thumbs up," he said.

"However, for our lambing friends, the farmers, who are doing the lambing season, it could be a tough go over the next few days over the South Island."

Weatherwatch is forecasting rain on Monday for those in Taranaki across to the East Cape, with thunderstorms possible. Heavy rain can also be expected on the west coast of the South Island.