Makgaputlane told the Herald a ridge of high pressure will be building today, which has displaced the warmer air mass from last week and replaced it with cooler air.
Queenstown and Masterton will only reach about 12C today.
Blenheim is looking at a low of 1C tonight, and Alexandra and Queenstown will face a low of 0C.
The North Island, Makgaputlane said, will get some sub-zero temperatures, and Taumarunui looks to be one of the coldest spots overnight.
She said those cold temperatures will soon become more frequent.
WeatherWatch is predicting tonight will be the coldest night of the year so far for those in Auckland. Overnight lows range from 7C in coastal areas to 3C for sheltered inland areas.
Hamilton could be in store for a light frost as it drops to 2C tonight.