Cyclone Gita is closing in on New Zealand. MetService says, as the storm moves over the South Island tonight, it will split in two.
A State of Emergency has been declared in Christchurch which includes Banks Peninsula.
The main storm will rage over the Banks Peninsula, while a smaller storm will hover over Westland.
A spokesperson says it's typical for the Southern Alps to divide low-pressure systems.
These are the things you need to know about the storm and where it could impact you.
It previously caused mass destruction in Tonga, and parts of Samoa and Fiji before making its way to New Zealand.
Gale-force winds gusting up to 120kph in Marlborough, and 130-140 kph are predicted for Nelson and Buller, Taranaki, Taihape, Whanganui, Manawatu, Kapiti-Horowhenua, Wellington and Wairarapa areas.
Heavy rain warnings are in place for Nelson and Buller from 9am Tuesday, with 150-200mm of rain expected to fall west of Motueka.
Civil Defence staff have been deployed to the areas that are expected to be worst affected, and are advising people to prepare for the possibility of power cuts, water outages and road closures.
People are advised not to travel during the storm, to prepare emergency evacuation plans and have a grab-bag ready.
Flights and rail cancelled
Air New Zealand has cancelled all flights in and out of Wellington from 2:45pm through to midnight on Tuesday due to severe weather in the capital.
Flights are also cancelled in and out of the following airports for the rest of the day - Hokitika, Nelson (from midday onwards), New Plymouth (from 11am onwards) and Queenstown.
KiwiRail's TranzAlpine service from Greymouth to Christchurch has been cancelled for Tuesday and Wednesday, affecting more than 1400 passengers.
They are being offered refunds or the option to reschedule their travel dates.
"We regret the inconvenience to our customers," said KiwiRail group general manager sales and commercial Alan Piper. "We are always striving to deliver the best possible service, but safety is paramount."
The last cable car in Wellington will run at 7pm.
State Highway 1 has been closed north and south of Kaikoura due to heavy rain, and the risk of slips and rockfalls.
Route 70, the inland road via Waiau, remains open for road access to Kaikoura. While crews will aim to keep it open as long as possible, drivers are urged to delay all but essential trips in the area until the severe weather has passed.
All drivers travelling from Picton to Christchurch are advised to take the Lewis Pass route, via Waipara and St Arnaud.
More than 40 schools and 17 early learning centres at the top of the South Island will be closed today.
"Schools and ECE services in the Nelson City, Marlborough, Tasman, Buller, Greymouth, Kaikoura and Westland districts have made plans overnight to close for the day or close early with severe weather warnings in place," a spokesperson says.
"We will provide support where and as requested for as long it is needed. In the meantime, we recommend parents and whanau check their school or early childhood service websites or Facebook pages, or contact them directly to get the most up-to-date information."