Severe weather warnings are in place across the country with heavy rain, thunderstorms and wind gusts expected to reach up to 150km/h in Canterbury and the lower North Island.
The Milford Track has been closed, and as the South Island's West Coast braces for torrential rain for the second time in a week, the East Coast's enjoying warm weather and strong northwesterlies.
As the front moves in from the Tasman Sea, MetService says the wet weather's trapped on the west side of the Alps.
“Imagine having a big, soaking wet sponge and you push it against the wall," says the MetService’s Dan Corbett. "That is the wall of the Alps. Squeeze it against the Alps, all the moisture comes out on one side, and that same air rises up and gets up over the Alps, but it's lost all of it's moisture."
The West Coast was battered by torrential rain last week, causing severe flooding.
Contractors have only just repaired the washed out Wanganui River Bridge on State Highway 6, and they're now busy securing the banks as river levels rise.
Forty kilometres south, trucks are dumping boulders onto the edge of the fast-flowing Whataroa River.
“With the ground already saturated we don't really need any more rain. In some spots across the West Coast we could see additional 300-400ml rain. Rivers will be flowing fairly quickly. All that rain falling as well is a risk for flooding,” says Mr Corbett.
Slips and road blocks are expected overnight, just as glacier country has started to fill up with tourists.
Winds up to 150km/h are expected in inland Canterbury and Wellington.
“[We have had] two or three weeks here without any substantial rain in those areas now in the Waiarapa and Hawke’s Bay. We'll be looking at elevated extreme fire danger conditions,” says national rural fire officer Murray Dudfield.
The front is expected to weaken as it reaches the North Island.