The second week of alert level 3 will see most of New Zealand blasted by a "nationwide cold change" with 10C temperature drops for some.
While there will be sunny spells for the next couple of days, MetService says heavy rain and strong winds are expected by the end of the week and into next week.
MetService meteorologist Andrew James said a trough moving up the country is behind the change and urged people to keep an eye on the forecast.
Auckland can expect rain from Saturday until early next week at least and in the south, Christchurch will get rain from Monday and a high of only 13C on Tuesday.
"Aotearoa sees a run of settled weather this week due to a ridge of high pressure. This is turned on its head come the weekend as a trough sweeps across NZ from the west," MetService said on Twitter.
The cold change will ease by the middle of next week, WeatherWatch reports.
It's predicting 10C drops for Invercargill (19C on Friday and 9C on Tuesday), Queenstown (16C on Saturday and 6C on Tuesday), while massive 12C drops are forecast for Dunedin and Christchurch.
WeatherWatch says western regions will "bear the brunt" of the systems. The South Island's West Coast can also expect rain from Saturday until at least Tuesday.
"This weekend severe weather warnings are possible in both islands as a storm in the Southern Ocean churns by," WeatherWatch said in a statement.