A once-in-500-year storm has slammed Northland, flooding shops and forcing residents to evacuate homes.
Fire crews rushed out to 212 emergency callouts as the storm dumped 220mm on Whangārei.
The heavy falls caused slips and landslides that closed roads and limited water supplies.
Whangārei residents were this morning being asked to conserve water after the city's water treatment plants were "struggling to cope with the intense rainfall", Whangārei District Council said.
Residents in Onerahi and Whangārei Heads were advised not to drink or use tap water except in emergencies after a burst water main on Riverside Dr drained local supplies.
Flood waters were now receding and MetService had cancelled severe weather warnings for Northland.
However, the Far North remained "effectively cut off" by road closures from the severe flooding.
Meteorologist Alwyn Bakker said the intense storm had been created by the unusual interaction between two low-pressure zones in a manner that caused a direct hit on Northland.
"We've done some calculations over here in MetService," Bakker said of the storm.
"And 220mm for Whangārei has what we call a greater-than-500-year return period."
"What that means is we see this kind of thing once in every 500 years."
Bakker said MetService's continued thunderstorm watch meant rainfalls of 40mm-60mm an hour could still fall this morning.
By the afternoon, however, the storm should break and turn to periods of showers later in the day before petering off tomorrow.
Central Whangārei CBD was quiet this morning.
Western Hills Drive (SH1) was closed. Signs saying there is no access north of Kaikohe are along the road.
Across town, surface flooding and slips partially blocked Whangārei Heads Rd in a number of places. Traffic control was working in one section of the road as workmen cleared a large slip.
Northland MP Matt King, a beef farmer who lives near Kerikeri, was among those caught in the storm.
He said a neighbour came to his rescue last night when floodwaters of more than a metre blocked access to his property.
He had to abandon his four wheel drive last night as it was not meant to drive through water more than a metre deep.
King said he was meant to put up election billboards today but instead will spend the day surveying the damage in his rural electorate.
A rescue helicopter had been called to the Far North to help a pregnant woman trapped by floods and slips on the roads.
College of Midwives president Nicole Pihema said the woman was 26 weeks' pregnant and in pre-term labour, but could not get to a hospital because of the storm damage.
She said a midwife made it into the town before the roads deteriorated and was doing everything possible to help.
"They were able to get access to the pharmacy and the pharmacist came in after hours and opened up and got access to drugs that they could slow the labour down and they were able to do that."
Pihema said it was a scary time for the mother, but the midwife was well-trained to handle such an emergency.
Civil Defence Minister Peeni Henare said the Government was also on standby to assist Northland residents, along with those in Coromandel and Tairawhiti who had also been affected by flooding.
"I've spoken to the local mayors and understand the most important message this morning is to stay off the roads and avoid unnecessary travel so that emergency services can provide assistance to those most in need," Henare said.
"As damage assessments take place this morning, I am considering options for travelling to the region to see where the Government can best support local communities during this time."
Murray Soljak, from Northland Civil Defence and Emergency Management, said fire crews carried the brunt of the emergency response overnight, rescuing people trapped in cars in floodwaters and helping evacuate people from homes.
He estimated about 30 people had evacuated homes across Northland, of whom 12 in Whangārei required assistance from fire crews.
Some relocated to the two Civil Defence welfare centres set up in the Kamo Scout Hall and Onerahi Community Hall.
Luckily, no one appeared to be injured, Soljak said.
Today would be all about making an assessment of the damage, putting priorities around that and seeing how long it would take to restore services, he said.
Between the flooding, damaged roads and slips, there was a lot to be done across the region this morning, he said.
He asked residents to stay off the roads today.
Civil Defence emergency management officer Claire Nyberg, who was manning the Civil Defence Centre at the Onerahi Community Hall, said she had been set up since 8pm yesterday.
Nyberg said only one person had been evacuated from their home and brought to the centre.
Nyberg, who had worked with Civil Defence for 12 years, said last night's rainfall was comparable to when tropical cyclone Wilma hit New Zealand and some Pacific islands in 2011.
The wild storms yesterday evening left a group of 12 stranded in waist-high swirling water at a flooded Whangārei petrol station.
The BP petrol station in Riverside Drive, Parahaki, was flooded after water started seeping under the door at 7.30pm. It is closed to the general public this morning.
A BP staff member there told the Herald a group of customers were stuck at the station.
"In the deepest spot it's probably waist deep. The whole place is pretty much under water. There's waves coming in the shop when people drive past and what not," he said.
The 25-year-old BP staffer said eight cars were stuck in the car park with water lapping at the sides about 9.30pm last night.
"Yeah pretty much [standing in water]. We've got a couple of customers here who are all trapped. So everyone here is pretty much trapped here at the moment," he said.
The staffer said the group of staff and customers stranded were calm.
"We ain't going nowhere. Everyone's pretty much chilling out talking and drinking coffee and eating pies," he said.
Floodwaters also hit The Real Cornish Pasty Company in Onerahi, south of Whangārei.
"It's at least halfway up my legs in the bakery at the moment," owner Derek O'Brien told the Herald last night.
Buckets and containers were also floating around the room, he said.
He said the floodwaters had come down the street, overwhelming the drains the council had cleared yesterday, and flowed under the doors of his business.
But by about 11pm, the floodwaters had receded, leaving a layer of sludge across the floor.
It meant O'Brien had been planning to transition into cleanup mode this morning rather than waking earlier to bake about 200 pies and pastries.
Northland hammered by thunderstorms, lightning strikes, huge tornado
Severe thunderstorms hit Northland all day yesterday, but Whangārei was struck particularly hard.
At 7.30pm, emergency services received multiple reports of people trapped in their cars because of flooding on State Highway 1 near Puketona in the Far North.
Today's wild weather: People trapped in cars, flooded homes abandoned in Far North, SH1 closed
Emergency services responded to more than 200 calls after flooded homes, people trapped in cars, a huge tornado and closed highways impacted the province.
Residents in the area were choosing to abandon their homes because of flooding.
"There has been heavy rain around the Whangārei area with multiple flooding events across the city," a Fire and Emergency spokesperson said.
"We recommend people stay safe in their homes and contact the local civil defence."
A resident in Cobble Lane, just off Rawhiti St in the Whangārei suburb of Morningside, said she could see people being evacuated from their homes near the hall.
It looked like they were wading through ankle-deep water before climbing onto a big truck of some sort.
Police and Fire and Emergency both confirmed they were attending an job on Rawhiti St as of 8.30pm.
Murray Soljak, of Northland's Civil Defence Emergency Management, said it was not a state of emergency but he expected it to be a very busy night.
MetService forecaster Gerard Bellam said Whangārei had received the biggest thunderstorm of the day just before 7pm.
"Unfortunately tomorrow we've got periods of rain. Some possibly heavy falls, and there are some thunderstorms again also possible north of Whangārei," Bellam said.
"In the meantime we've nearly had about 50mm in the last hour in Whangārei airport just before 7pm. That's another thunderstorm."
Rain flooded parts of State Highway 1, closed roads between Okaihau and Kaitaia and at Moerewa near Bay of Islands.
Niwa reported 500-plus lightning strikes in Northland yesterday, and 125mm of rain in the Far North.
Elsewhere, a video of a huge tornado out at sea was filmed near Tupou Bay in the Far North after midday.
Bellam said the weather in Northland was forecast to be bad again today.
- with RNZ