MetService has also issued road snow warnings overnight Tuesday for Lewis Pass, Arthur's Pass, Porters pass, Lindis Pass and the Crown Range Rd.
As the front moves on to the North Island tomorrow, gale-force southwest winds will envelop most areas.
James said there was "high confidence" of severe west to southwest gales – over 85km/h, with gusts even higher – from Northland, Auckland to Taranaki and eastwards to East Cape early tomorrow. Exposed parts of Wellington, Marlborough and Kaikōura would also be affected.
Widespread showers and periods of heavy rain across the North Island were also forecast ahead of the front tomorrow.
The Auckland region would see southwesterly winds and some showers today, before both the wind and rain picked up rapidly on Wednesday morning.
The North Island's west coast would also see southwest swells in excess of 5m, James said.
"This is going to be quite a significant event. On land we are warning people to take precaution from the high winds, don't leave anything loose outside. And at sea there are going to be some very large swells."
Weatherwatch NZ said these ocean swells could produce waves in excess of 9m in places, driven by "hurricane-force winds" at times.
"This makes for dangerous marine and beach conditions along the western side of the country, in particular the western side of the North Island which is more exposed to this set-up.
"There will be rogue waves that may go higher too - so a warning in particular to Aucklanders who fish on the western rocks: this isn't a safe week to do so.
"It's not a safe week for boaties anywhere in the eastern Tasman Sea area or Cook Strait."
