Horrendous weather will lash most of New Zealand today as major highways in the South Island remain closed and a state of emergency is declared in some areas because of intense downpours.
Flooding is now starting to affect Wellington where emergency services are dealing with multiple calls.
And Spark is battling to restore internet to a large part of the South Island after fibre cables were cut in the storm.
"All Spark mobile, landline and broadband customers south of Ashburton are affected," said a spokesperson.
"However, mobile phones can still make 111 calls and we encourage people to check on neighbours who may not have access to mobile phones."
The Herald will update the situation as it unfolds.
The Government has declared a "medium-scale adverse event" for South Canterbury, and has set aside up to $50,000 to support farming communities significantly affected by heavy rain and flooding.
Agriculture Minister Damien O'Connor said this afternoon that two weeks of solid rain had put tremendous pressure on farmers.
"They need to know that the Government is there to support them," he said.
The severe weather had affected milking and pick-ups, and damaged pasture, fencing, races, stock water and irrigation systems.
Officials have yet to determine the full extent of the damage.
"The West Coast received $30,000 for a flood in May and some of that funding is still available. We will assess whether more is required over the coming days."
Police said State Highway 72 near Arundel in the South Island remains closed because of flooding.
State Highway 1 is also closed.
Workers are trying to clear the roads but because of the massive job, they will be closed for the coming days.
Motorists are asked to avoid the area.
Spark has confirmed "almost all" of the affected South Island broadband, mobile and landline services have now been restored.
"This has been achieved by a work-around using spare fibre strands and additional cables," Spark posted on Twitter.
"While the restoration of services is good news, it's important to note services are still vulnerable as they are reliant on a damaged cable, which could be affected by weather conditions.
"Our team will continue to monitor the situation and share further updates ASAP."
Chorus have given further information on the faults on the network throughout the South Island affecting broadband, landline and cellphone coverage.
Spark, Vodafone, 2degrees and Vocus use Chorus' wholesale network for their landline service.
"The main areas impacted are in Geraldine and Ashburton," said a Chorus spokesperson.
"A section of fibre has also been damaged in Fox Glacier on the West Coast following a large slip.
"Repair work is already under way in many areas however, due to slips and flooding, technicians are not allowed to access some areas due to the current State of Emergency.
"Technicians are ready to start repair work in these restricted areas just as soon as they are given permission from officials.
"Chorus apologises to those impacted by the outages and is working as quickly as possible to get services back up and running."
Just before 8am Spark said fibre cables had been cut in two places.
Technicians are testing replacement cables.
"We'll be updated as soon as anything changes and will let you know as soon as we are aware. Thanks for your patience," the company posted on Twitter.
Last night Spark said customers were experiencing broadband and mobile outages because of flooding and slips across the South Island, but technicians were unable to get there because of road closures.
"Our team is working hard to resolve the situation and we apologise to our customers for the inconvenience. We will share more information with you as soon as possible."
A Fire and Emergency spokesperson says they've had about 25 flooding-related calls in Wellington since about 6am.
The weather has also forced police to cancel a planned firearms collection at the Kennell Club in Porirua.
"Because of flooding causing road closures many of our staff are unable to get to the event to man it," said a police spokesperson.
"Some staff will be at the Kennel Club this morning to advise people who do make it there, that the event has been cancelled.
"We apologise for any inconvenience this may have caused."
A crash has closed State Highway 58 and landslips and debris are obstructing the route.
Flooding has closed State Highway 2 northbound from Kelson and SH1 at Plimmerton.
Firearms collection in Porirua has also been cancelled because of the weather.
Internet is not the only thing cut off in the south.
State Highway 1 has been closed, cutting off the main route between Christchurch and Dunedin, and residents in Timaru were told to evacuate as the local river rose to dangerous levels for the first time in 20 years.
The Timaru District Council this morning said the SH1 Bridge at Rangitata will remain closed this morning.
"NZTA are inspecting but access is still limited so it's unlikely it will open in the near future," said a spokesperson.
"SH72 will remain closed until further notice, there's significant water and damage to the approaches, so we are unable to inspect the bridge at this point."
The closures are likely to cause havoc for many road users.
And for the rest of the country, the weather hell is not over yet.
The slow-moving front responsible for the carnage will this morning stall over central New Zealand, bringing the risk of more heavy rain to parts of the North and South Islands, MetService meteorologist Cameron Coutts said.
A cluster of thunderstorms hit Wellington overnight, sending residents to social media to share photos and video of the impressive light show.
Aucklanders can expect isolated showers, more widespread from midday, with thunderstorms and possible downpours.
Then, there will be northwesterlies, strong in exposed places, from afternoon.
For all of the North Island apart from Gisborne and Hawke's Bay, scattered showers are expected, along with some heavy with thunderstorms, hail and possible downpours.
In Gisborne and Hawke's Bay the situation will also be grim with rain about the ranges, possibly heavy and thundery.
An scattered showers should start spreading east of the Hawke's Bay ranges from the afternoon.
There was an orange-level heavy rain alert, with possible thunderstorms warning for Westland, from Otira south, in the 10 hours to 11am today.
Heavy rain watches are in place today across a large swathe of the central and lower North Island, and parts of Nelson and Marlborough.
But of particular concern was the risk of more downpours in Canterbury, with a heavy rain watch issued for the headwaters of Canterbury lakes and rivers about and south of Rakaia River, in the nine hours to 11am today, Coutts said.
Yesterday afternoon, Timaru District Council told all those living between McLelland, Orion Rangitata Mouth roads and Rangitata River to evacuate immediately.
The order was given after a one-in-20-year flooding of the Rangitata River blocked off State Highway 1, with the water coming down the river peaking at 2700 cubic metres per second, Timaru Emergency Operations Centre's Steven Doran said.
"The river usually runs at about 300 [cu m/s) so it's a big, big difference. It's a braided river so it doesn't always flow in the same path as well. So it can change path, and a lot of farmland can be in the way as well."
The flooding near Timaru, and also on the West Coast, blocked all road routes between Christchurch and Dunedin yesterday and overnight. State Highway 1 and Route 72 between Ashburton and Timaru are closed.
State Highway 6 on the South Island's West coast was closed from Hokitika to Makarora, because of several slips. Settlements on the highway were cut off from each other because of the damage.
More than 350km of the highway was shut because of the slips and a bridge washout, New Zealand Transport Agency system manager Pete Connors told RNZ.
"The real problem we've got is between Fox Glacier and Franz Josef - on what we call the Fox Hills ... there's been some pretty substantial slips."
He didn't know how long it would take to repair the roads.
Power was also out from Fox Glacier to Paringa, and was likely to remain so for a couple of days.
A spokesperson for Westpower said the lines company was working with Civil Defence and roading authorities to find out when they could get in to replace downed power poles.
Meanwhile, in Wanaka yesterday, sandbags and black plastic sheets were covering the fronts of most businesses along Ardmore St and Queenstown Lakes District Council shut down the street's sewerage system amid fears of Lake Wanaka flooding.
Yesterday afternoon lake levels remained about 25cm below the flood alert threshold.
Today would be unsettled across much of the country, Coutts said.
Thunderstorms were possible in the upper North Island, including in Auckland and Hamilton.
But a cool change on Monday, and especially Tuesday, would start to turn off the tap.
"The whole country's going to be [experiencing temperatures] below average on Monday as the southerlies start to push across the country.
"Tuesday's looking pretty good for most of the country as finally we get rid of the northwesterlies."
- ADDITIONAL REPORTING: Cherie Howie