Photo: RNZ / Rebekah Parsons-King
Auckland could see thunderstorms, hail and wind gusts of up to 90 kilometres an hour this evening.
Northland, Waikato and Waitomo also had a moderate risk of thunderstorms, MetService said.
"A low west of Taranaki is expected to move northeast during the day and lie over Auckland or northern Waikato tonight," it said.
"Cool temperatures in the upper atmosphere over the North Island and northern South Island make conditions unstable in many places.
"There is a low risk of thunderstorms during the day, but especially this afternoon and evening, about most of the North Island and the western Tasman District."
MetService on road snowfall warnings in the South Island
"Particularly heavy rainfall" was possible for eastern and central parts of the North Island.
Overall, MetService said there was "minimal chance" of severe weather this week.
On Tuesday, MetService said high pressure would build over the lower South Island, with a "cold showery southerly flow" affecting eastern parts of both Islands.
On Wednesday, that high pressure was expected to move eastwards, and the cold winds should ease up.
MetService said Thursday could see it continue to move east with a new front approaching the lower South Island, creating a "moist northerly flow".
By Friday, the west coast of the South Island could possible see heavy rain, it said.
"At this stage, however, there is minimal risk of severe weather."
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