A severe low pressure system is lashing the lower North Island and upper South Island, with 21 warnings and watches in place across the country.
In Christchurch, the Avon River has burst its banks near the CBD, while further south, a state of emergency has been issued in south Canterbury district of Selwyn, with limited evacuations and flooding prompting the closure of schools.
The biggest threat is in the capital, where dorecasters MetService are warning of threats to life and property, urging people in exposed areas and on the south coast to stay home.
"Threat to life from flying items and falling trees. Destructive winds will cause widespread damage including powerlines and roofs, with dangerous driving conditions and significant disruption to transport and power supply," their warning states.
"Stay indoors or seek shelter, avoid travel. Be ready for power and communication outages."
It is the first red weather warning issued in New Zealand since flooding in Dunedin in October 2024, and a first red warning for wind in Wellington since the system's introduction 2019.
"Wellington is no stranger to high winds but even by our standards this is an extraordinary day in the capital," MetService meterologist John Law told AAP.
Mr Law said the "combination of wind direction, a strong sotuherly, and rainfall and higher tides" has prompted the warning escalation.
The highest gust was recorded at Mr Kaukau, an exposed point in the city's north, at 150km/h, with the airport on the south coast registering 115km/h, prompting flight cancellations.
The vicious southerlies are predicted to pick up through the day, subsiding later on Thursday - though swells are expected to stay large.
Cook Strait ferry operators have also cancelled sailings through to Friday at the earliest.
The huge storm has also brought the first major snowfall for the season further south, with news outlet Stuff publishing pictures of a thick snow blanketing the inland town of Tekapo.
16°C