Auckland and Northland are forecast to be at the receiving end of thunderstorms and possibly heavy rainfall around midday.
Thunderstorms and heavy rain are expected over western and central parts of the North Island over the next few days as a complex low-pressure system slowly moves over the country.
This afternoon a northwesterly flow will cover the North Island with an "embedded trough and warm front" that will move over the northern and central North Island.
There was a moderate risk of thunderstorms within broader areas of rain about western parts of Northland, Auckland, Waikato and Waitomo during the afternoon, as well as the eastern Bay of Plenty in the afternoon and early evening.
MetService meteorologist Brian Mercer said last night there were a few thunderstorms reported on the east coast of the North Island but they moved away before long.
This morning there was "an active band moving towards Auckland and Northland, bringing thunderstorms around midday".
"Heavy rain and possible thunderstorms are expected from 9pm last night to 9pm Thursday, it is a broad time because it is a slow-moving feature.
"There could be some significant rainfall to come with this."
Tongariro National Park had already received 30 to 50mm or rainfall overnight, Mercer said.
"They are continuing to get 3 to 5mm an hour and that is expected to continue through the day, easing by the afternoon."
These thunderstorms would be accompanied by localised heavy rain of 10-20mm/h and small hail.
Additionally, the thunderstorms may be squally about Northland, Auckland, Waikato and Waitomo with gusts of 80-100km/h.
A heavy rain watch is in place for Taranaki and the King Country, including the Tongariro National Park until 9am Thursday.
Heavy rain and possible thunderstorms were expected during the watch, especially Wednesday afternoon and overnight. Rainfall may reach warning criteria at this time.
Snowfall warnings were also in place for the Desert Rd, State Highway 1, Lewis Pass, SH7 and Milford Rd, SH94, until 11am Thursday.
"Snow showers are expected about the tunnel overnight tonight and Wednesday morning. Between 11pm Tuesday and 11am Wednesday 2 to 5cm may accumulate about the tunnel, with lesser amounts to 700m."
This morning in the North Island the Desert Rd was at freezing temperature recording 0C, while Taupō was at 4.5C.
In the South Island, Pūkaki recorded -3.2C, Christchurch Airport recorded -1.3C while Alexandra in Central Otago was a chilly -1.1C.