Swells of up to 6m battered the Napier coast yesterday.
Unusually large waves forced cyclists to slosh through the water while cars were lucky to escape with just a wash.
Napier bore the brunt about midday with waves pushed over the Rotary pathway.
A big low pressure weather system had been driving the heavy seas between East Cape and North Canterbury, with Wellington hit hardest.
MetService meteorologist John Law said the swells should subside today with a high pressure system due to take over.
Strong southerlies from the Antarctic were also contributing to the rough seas, Mr Law said.
Napier City Council spokesman Lance Titter said there had been no reports of damage.
The council would monitor the situation overnight, co-ordinating with Napier police, Mr Titter said.
Temperatures in Hastings are set to plummet to freezing again overnight, a chilling reminder winter is just around the corner.
The brisk mornings will continue until the weekend when the system bringing the southwest chill moves east.
Mr Law said the weekend should warm up, with temperatures likely to reach 17C.
"A northwesterly flow will gradually spread up the country ahead of a weather front." The front is expected to approach the South Island on Friday then move up the North Island on Saturday and Sunday.
"Hawke's Bay is not a bad place to be at the moment," said Mr Law.
Other than the odd shower around the Cape and Mahia, the Bay would remain dry until late this week: "There is a chance of some high cloud and scattered showers on Sunday."
Monster waves pound Otago coast
Ten-metre waves, whipped up deep in subantarctic waters, crashed into the Otago coast yesterday, preventing ships from entering the harbour and giving Dunedin beach defences a good workout.
The giant waves were breaking behind and over White Island off St Clair Beach, although the Esplanade appeared to have stood up to an onslaught at high tide, shortly before noon.
Department of Conservation ranger Colin Facer said he had been working at Taiaroa Head for 16 or 17 years ''and that would be the highest [seas] I would have seen''.
That sentiment was shared by Port Otago chief pilot Captain Hugh Marshall, who said: ''That's probably about right.''
The waves started to increase in size on Tuesday evening, but it was not until yesterday morning they began to affect vessels.
Capt Marshall said the Iver Express was delayed and was forced to wait off-shore until the conditions settled. It was expected to be there overnight.
The Port Otago vessel schedule showed three more vessels due between 4am and 9am today.
Capt Marshall said one issue was the easterly direction of the waves, which were breaking on the sandbar at Taiaroa Head.
''There's so much energy in that system that's coming from the south.
The wind's died down, but the swell's just continuing on.''
He hoped conditions would be calmer today.
MetService meteorologist Georgina Griffiths said the mean wave height off the coast was about 5m, with the ''occasional 10m running through''.
''Obviously, you've had five days of southerly gale or storm from Saturday in Otago, but it's eased off today.''
However, not all the waves were a result of the weather being ''really, really windy''.
The recent large low pressure system that brought snow to Dunedin had a long ''fetch'', or area of ocean surface affected.
The low had stretched to the subantarctic area, about 800km to the south.
''What we're actually seeing on the coast today is the longer waves coming from well south of New Zealand.''
The low had moved, but the big waves generated days ago when the low was south of New Zealand were peaking yesterday morning.
''They're really grunty; they've got a lot of energy associated with them.''
Erosion at St Clair closed a walking track this week, but Dunedin City Council parks manager Lisa Wheeler said there were no reports of further damage yesterday.
Huge waves and powerful winds scattered debris and stopped traffic on coastal roads in Wellington yesterday, NZME reported.
In the South Island, high tides and big swells blocked parts of State Highway 1 in Kaikoura.
The big swells in Cook Strait disrupted plans for some Interislander ferry passengers.
The 10.45am Aratere sailing from Picton was cancelled, and the 2.45pm sailing from Wellington was freight-only.
- Additional reporting by David Loughrey, Otago Daily Times