It's a wet day for the country on Sunday with heavy rainfall amounts that could approach 50mm in some areas.
"A slow-moving front lies across central Te Ika-a-Māui / North Island today and overnight tonight, bringing bursts of heavy rain and thunderstorms," MetService says.
The forecaster has watches out for severe thunderstorms and heavy rain, with a moderate risk of thunderstorms for Waikato, far western Bay of Plenty, Coromandel, Auckland and Northland.
"Any thunderstorms that occur are expected to bring localised heavy rain 15-25mm/h and be slow-moving," it says.
"Consequently, there is also a moderate risk that these thunderstorms may become severe and deliver localised downpours (25-40mm/h) or possibly even torrential rain (greater than 40mm/h). A severe thunderstorm watch has been issued for these areas."
And next week will see even more rain as a tropical cyclone exiting the tropics links up with a larger but weaker low over New Zealand.
While this will suck energy from the cyclone and reduce its power, WeatherWatch warns it can give more fuel to the low over New Zealand - encouraging more rain and blustery nor'easters.
"In a nutshell, this week coming up will be warm, humid, wet and cloudy for the North Island and upper South Island. Classic La Niña set up with the risk of torrential falls in some North Island regions," WeatherWatch head forecaster Philip Duncan says.
"On Tuesday, a moist north to northeast flow is expected to lie over northern and central New Zealand ahead of a low-pressure system approaching from the north," MetService says.
"On Wednesday, the low should move slowly southeastwards over northern and central areas while deepening, before moving away to the southeast on Thursday. This low is expected to bring significant rain and strong winds to many areas."
On Tuesday and Wednesday, MetService says there is a moderate confidence of warning amounts of rain about the ranges of eastern Bay of Plenty and Gisborne, Mount Taranaki, northwest Tasman, the Marlborough Sounds including the Richmond and Bryant ranges, and the Kaikoura Coast and Ranges.
