MetService has issued orange severe weather warnings, with heavy rain predicted for the north-east of the North Island.
Meteorologist Ngaire Wotherspoon told Morning Report that it would be a "wet and windy start, for a more unsettled week".
A frontal system was moving south-east over Aotearoa today, and this was expected to affect northern and central parts of the country.
It had arrived in Northland overnight, and was spreading downwards through Auckland at dawn, Wotherspoon said.
NZ Transport Agency said a strong wind warning was in place on the Auckland Harbour Bridge until about 1pm.
"It is likely that speed limits will be reduced and some lanes on the bridge could close if wind gusts reach threshold levels.
Motorists are urged to drive to the conditions and look out for the electronic message boards which will indicate lane closures or full closures (depending on wind thresholds) and reduced speeds, and stay within their lane while travelling across the bridge."
NZTA also advised motorcyclists and drivers of high sided vehicles to avoid the Harbour Bridge and use the western ring route on State Highways 16 and 18.
MetService issues rain, wind warnings
An orange heavy rain warning is in place for the Coromandel Peninsula from 8am to 10pm on Monday.
Up to 100mm of rain was predicted, and MetService warned that streams and rivers may rise rapidly, with surface flooding, slips and difficult driving conditions.
"Definitely keep an eye out if you're heading out on the roads," Wotherspoon said.
Thames-Coromandel District councillor Deli Connell, from the Mercury Bay ward, told RNZ it had been blustery and showery with the odd downpour, but urged visitors to still head to the region in the coming week.
"The modelling suggests that it's going to blow through quite quickly. It's certainly not a [Cyclone] Gabrielle [event], if people are panicking.
"Please don't cancel your holiday plans, because the rest of the week is looking really, really good."
The Bay of Plenty west of Kawerau should also brace for heavy rain from noon until 4am on Tuesday, after the MetService issued an orange rain warning there, with up to 110mm of rain inland and up to 80mm on the coast.
The following places would also see a period of heavy rain, but this was not likely to get to warning levels, MetService said.
- Northland until 2pm Monday, with heavy showers and thunderstorms likely to develop after heavy rain.
- Auckland north of Whangaparaoa Peninsula, from 6am Monday to 4pm.
- Bay of Plenty east of Kawerau and Gisborne/Tai Rāwhiti north of Ruatoria, from 6pm Monday to 6am Tuesday.
- Tasman District, around and east of Motueka, from 5pm Monday to 3am Tuesday.
Meanwhile, it was a frosty start for many in the South Island this morning, with some areas dipping to freezing temperatures.
The coldest place overnight was Alexandra, dropping to minus 5.9 degrees.
Invercargill and Queenstown were both sitting on minus 3 degrees.
For the rest of the week, some weaker frontal systems would be moving across the country, bringing more rain and unsettled weather, Wotherspoon said.