Snow is starting to fall on the hills surrounding Wellington after an "intense" hail storm hammered areas of the capital in the early hours.
Heavy surf is also hitting the south coast.
Snow is now being reported to have been seen by people in parts of Karori and Johnsonville.
The New Zealand Transport Agency is warning motorists that snow is now starting to fall on the Remutaka Hill and likely to continue for the rest of the day.
The icy hail blast came as the vanguard of a polar blast sweeping up the country from the south.
With snow blanketing much of the south, leaving numerous highways closed and even falling to sea level in Christchurch overnight, attention is turning to the north, which is starting to feel the brunt of the polar air.
Twenty flights have been cancelled at Wellington Airport this morning, with an airport spokesman saying that they are regularly inspecting their runway and seawalls as heavy swell batters the coast.
MetService has also advised that snow is expected to affect SH2 at Remutaka Hill through to this evening.
They warned 4-8cm of snow may settle near the summit of the road, with lesser amounts down to 300 metres.
The Wellington Region Emergency Management Office (WREMO) said they expected the swells to be at their heaviest at 9pm, and were preparing for the expected impacts on Tuesday evening.
They advised on their Facebook page that people on the Wellington South Coast, and south and east Wairarapa Coast be prepared for heavy swells and waves.
Two kayakers have been located safe after reported missing off Wellington's south coast this morning.
Police were alerted to a kayaker, who was possibly in distress, off Marine Parade in Seatoun just before 8am.
"Police received a report at 7.55am that someone had witnessed a kayaker in possible difficulty off Marine Parade," police said.
"A second kayaker was also in the area and was seen paddling towards the first. The person making the report then lost sight of the two kayakers, but it is believed they may have been heading towards Eastbourne."
The Police Maritime Unit, Coastguard and a rescue helicopter were also assisting with the search effort. The kayakers where reported safe on land in Petone at around 9.30am.
Speaking to the Herald at Owhiro Bay, Wellington mayor Andy Foster said the conditions were so far better than expected.
"We're not seeing any debris across the roads so far, which is a good thing," he said.
"And if there's no debris across the road it's not hitting the houses, which is obviously our biggest concern."
He said their another concern was for Tuesday night, when the next high tide was expected to bring greater wave heights.
"The advice is still there at the moment, which is batten down the hatches, keep pets inside and anything that's likely to blow away," he said.
"And just be prepared with the grab bag if you're one of those properties that have been affected before, just in case you need to evacuate."
Brooklyn Resident Fraser Smith had come down to Owhiro Bay to see the big swells on Wellington's south coast, and said it had been getting bigger as he had driven down the coast.
"The swells are definitely picking up, especially with the high tide about now, but these swells seem to be getting closer to the foreshore," he said.
"I think road evacuations maybe road closures might be later on."
WREMO acting regional manager Daniel Neely said the waves are likely to increase at high tide later this evening.
"The impact of these large swells are likely somewhere between what we experienced in the Owhiro Bay event last year and the Matariki storm of 2013."
Neely said from 9pm tonight they are expecting water to start breaching onto the roads.
He warned people to stay vigilant around the coast, avoid the coastal areas if you can and for people living around coastal areas to secure their homes.
An update for the swells is likely to be released around 5pm today, he said.
The polar blast brought snow to sea level in parts of the south yesterday, as well as huge seas and gales laced with a bitterly cold -20C windchill.
An active cold front and south-to-southwesterly winds will track north across the remainder of the country, with numerous weather warnings in force.
Heavy snow was possible in Taihape, around the Tararua Range and Banks Peninsula today.
A road snowfall warning is in place for the Napier-Taupō Rd (until midday Tuesday), Desert Rd (until 5pm Tuesday) and Remutaka Hill Rd (until 4pm Tuesday) in the North Island.
Residents in Wellington shared photos of the hail, saying they had been "pummelled" by the sudden downpour.
"The hail was the size of small marbles. I've never seen anything like it in the time I've been here," wrote Khandallah resident Brad Markham.
In Wellington, snow is forecasted to 300m with the chilly high of 8C and low of 6C while strong southwesterly and gale winds gusting to 90km/h are expected.
In Auckland, a high of 13C and low of 4C is on the cards, with frequent showers in the morning, possibly turning heavy before clearing to fine weather in the afternoon.
The rain clouds will clear by Wednesday but the temperature would stay cool in Auckland, with a high of 14C for the rest of week and lows of between 4C-6C.
The weather is less severe in Whangārei today, with a few showers forecasted before clearing and turning fine.
Meanwhile, as one part of the country is coated in snow, those in Horowhenua are facing the possibility they may run out of water.
The Horowhenua District Council has pleaded for thousands of residents in Levin, Tokomaru and Shannon to reduce or stop using water immediately.
Due to the recent rain, water-treatment plants have struggled to effectively treat the muddy river water for the region's drinking water supplies.
"If residents don't act to reduce water usage or stop completely if they're able, there is a real risk that the water supply will run out and the community will need to rely on bottled water or water tanker supplies to service their minimum requirements," the council said.