Thunderstorms bringing large hail and damaging winds are possible parts of the western North Island today, MetService says.
The worst of the storms are expecting to come in from the west, hitting the western Manawatu, Taranaki, the western Waikato and north to about Raglan.
These storms could bring downpours of more than 25mm per hour, damaging wind gusts of more than 110kmh and large hail more than 20mm in diameter, Metservice said.
Lesser, but still serious storms, will make their way further inland and further north, possibly affecting Auckland, Northland, Coromandel, Bay of Plenty, Taupo, Palmerston North and the Kapiti Coast.
A few storms may make it across to the eastern side of the North Island, affecting East Cape, the Hawke's Bay ranges, Wairarapa and Wellington.
MetService maps showing forecast thunderstorms over New Zealand on May 25, 2018.
In the South Island, the western parts of Nelson Tasman and northern West Coast have a moderate risk of storms, while there is a low risk for the rest of the West Coast, Stewart Island, Southland, Marlborough, Kaikoura and the northern Canterbury area.
Later today, a moderate risk of thunderstorms will remain across a large part of the North Island, including Northland, Auckland, Coromandel, Waikato, Taranaki, Waikato, Bay of Plenty, Central Plateau and Manawatu - a low risk will remain for the rest of the North Island.
Any thunderstorms this afternoon in the South Island are likely to be along the eastern coast.
Road snow warnings are currently in place for the Desert Road, Lewis Pass, Arthur's Pass, Porter's Pass, Haast Pass, Lindis Pass and Milford Road.
The Crown Range road, Lewis Pass and Arthur's Pass are closed to traffic.