It will also be slightly colder during the day, going from 23C to 20 from Wednesday until the weekend.
Orange heavy rain warnings are in place Fiordland, Westland about and south of Otira and the headwaters of the Canterbury lakes and rivers, about and south of Arthur’s Pass from Monday morning.
MetService said 210 to 260mm were likely to accumulate about the ranges, and 70 to 120mm near the coast. It said peak rain rates could be up to 35mm an hour in the ranges, and thunderstorms were possible.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
Heavy rain watches are also in place for Southland and Clutha, Canterbury, Banks Peninsula, Otago, Westland north of Otira and Buller, the headwaters of the Otago lakes and rivers and Stewart Island.
These areas will see periods of heavy rain with amounts that may reach, or possibly exceed warning criteria on Monday and Tuesday.
“That front is going to start spreading onto the North Island on Tuesday and so those north-westerly winds in the usual places like Wellington will be quite strong ahead of the front,” said Miller.
Lower parts of the North Island can expect a change to strong south-westerlies behind that front.
“The front should start clearing away from the North Island on Tuesday evening and the south-westerlies on the eastern parts of the South Island and lower North Island will start easing on Wednesday morning,’ Miller said.
The country will see more settled weather after that as a ridge of high-pressure starts building in the Tasman Sea.
“Wednesday and Thursday are looking fairly settled over much of the country,” Miller said.