Heavy rain watches are in place for parts of the North Island, with forecasters warning "lows after lows" are forming in the Tasman Sea.
A heavy rain warning is in place for the Bay of Plenty ranges east of Ōpōtiki from 6pm on Tuesday until at least 4am on Wednesday. Heavy rain watches were also in force in Northland and Mt Taranaki, and Auckland might be in the firing line too.
"The Tasman Sea area looks about as busy as the Southern Ocean with low after low forming there and crossing NZ in the coming week and a half," WeatherWatch said in a statement.
MetService has warned rainfall in Northland could prompt its heavy rain watch to be upgraded to a 'warning'.
"For Northland, there is moderate confidence of warning amounts of rain from Wednesday to Friday," MetService said in its severe weather outlook. "For Auckland and Coromandel Peninsula, there is low confidence of heavy rain during Thursday and Friday."
WeatherWatch said the forecasted lows were expected to bring bursts of rain and wind across New Zealand during the next 10 days.
"Not all lows are stormy but at least three produce some severe weather risks in both islands," the forecaster said.
"For northern NZ the sometimes mild airflows pulled out of the Tasman Sea or sub-tropics may mix with colder air moving in from the south, producing isolated thunderstorms next week - and/or pockets of heavy rain."
There were also warnings of snow for the lower South Island but it will largely be confined to the alpine roads and passes.
Still, the deep south had "true mid-winter weather on the way with a large high-pressure zone later this week also helping contribute" to the freezing air, WeatherWatch said.
Alexandra in central Otago was only expected to reach a high of 4C on Thursday, according to MetService.
