Much of the North Island will drop below freezing overnight with Taupō forecast to hit -4C as a blast of cold southern air brings unseasonable frosts just hours after the spring equinox.
The equinox, which fell today, marks the point when day and night are roughly equal in length, but a blast of cold southern air means the season will start with frosts.
MetService forecaster Chelsea Glue said the North Island would bear the brunt of the cold tonight.
"We're going for below-zero temperatures for many places in the North Island tonight, frosty conditions," she told 1News.
Taumarunui was forecast to plunge to -4C, Rotorua to -2C while Hamilton and Whakātane both hit -1C. Parts of Auckland were expected to get down to 3C.
Glue said the temperatures were "quite cold for this time of year" for the North Island.
"Normally [they're] starting to get a little bit warmer this time of year, but a few late-season frosts are still in the cards for them."
Glue said a cold change moved up the country today, bringing southerly winds and a colder air mass from the south.
"As the rain and the cloud starts to clear away to the north, we're left with clear skies and that allows for temperatures to drop overnight."
Cold air from the south
In the South Island, Christchurch is forecast to reach -2C and Blenheim -1C.
"They're probably a little bit more used to the colder temperatures down there, so it's not quite so unseasonable for them," Glue said.
Nelson is expected to fall to 1C, which Glue said was "pretty chilly" for the region.
"Just when you're starting to think you're getting into fruit-growing season, you've got to be mindful of these frosts coming in."
Heavy showers and lightning strikes had been recorded offshore today, but MetService expects them to ease tonight.
Glue said many places would see fine, clear skies tomorrow, although showers would linger in parts of the far south.
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