As rivers and streams burst their banks, roads, homes and businesses in Kapiti, Porirua and the Hutt Valley were seriously flooded in many areas.
As the morning commute started, a slip blocked part of State Highway 1 on the Kapiti Coast.
Commuter chaos followed as the highway between Paekakariki and Pukerua Bay was closed and detours were off-limits as slips and flooding struck the Paekakariki Hill road.
Flooding also hit areas south of Waikanae.
The morning misery intensified as streams surged and some residents had to leave homes in Moa and Tui roads in Raumati.
The Emergency Management Centre in Paraparaumu was activated and an evacuation centre set up at Te Newhanga Kapiti Community Centre, with Raumati South School on standby. In Lower Hutt, flooding hit the city's main road before noon. Workers were on the street as waters rose and roundabouts were submerged.
Coronation Coffee owner Indra Sinnathambi said he'd never seen a deluge so severe.
Professionals real estate employee Gareth Barlow said water was knee-deep on the street and seeping inside his office.
"There's a 5m pond in front of us. People ... have had to take their shoes and socks off and roll their pants up to wade out," he said.
Surface flooding hit the local Work and Income office, and a staff member said all clients had to leave when water poured inside.
Back on the Kapiti Coast, Raumati Beach resident Jane Bly said a creek on her property burst its banks.
"Our backyard is completely underwater," she said. "We've lived here for 18 years and it's flooded once before but I've never seen it like this."
Nearby, Jeffrey Gardiner said a creek behind his property was four times its usual size.
MetService meteorologist John Law said Paraparaumu, also on the coast, had about 100mm of "incredibly intense bursts of rain" in just 12 hours.
Paraparaumu resident Alana Smith said she was amazed how fast her house filled up with water.
"My first impression was holy hell, that's bad."
Her neighbour Justin Patterson had a rude awakening as his feet reached for the floor of his home.
Greeted with a cold gush of water, he turned on the light to find his Mahana Rd house a foot deep in water.
"I said five F-words in a row and thought ... Well it's happened, I might as well live on with it."
For children of Mazengarb Rd, a regular school day was replaced with stomping, splashing, and free boat rides.
"It was actually really fun to have all the neighbours in one place saying hello to each other," local mother of four Jacqui McKenzie said. "How often can you row down your street on a boat?"
The deluge forced the Kapiti council to offer sandbags to affected households. It was soon clear the sandbags were in short supply.
Otaihanga resident Alastair Beissel spent the morning sand-bagging his and nearby properties.
"I went out and grabbed whatever I could, like potting mix bags and put them round the house to keep the water out," he said.
Nearby, Vivienne Bould put sandbags around her house and had a load of sand dumped on her driveway.
"The sewage pumps aren't working. I don't know whether that's because the rivers have flooded into them up."
On the Waikanae River, which burst its banks, a man was rescued on the bucket of a digger. Kapiti mayor Ross Church said the man was trapped in mud.
A cyclist also needed rescuing when he was caught in the river's floodwaters.
Flooding hit Tawa too, as the Porirua Stream surged.
Disruption to commuters intensified as SH1 from Petone to Melling was closed, all train services were suspended and Wellington train station was shut.
By 3.30pm, Civil Defence authorities said Porirua, Kapiti Coast and Hutt Valley residents should mull an overnight stay in Wellington.
"Now might be a good time to get to know your workmates a bit better," said Bruce Pepperell, Wellington regional management office group controller.
Wellingtonians offering accomodations
Generous Wellington residents offered accommodation on a Facebook page set up after the flooding.
Erica Challis of Brooklyn offered a room on the ""Stuck in town tonight - Wellington" page.
She said she'd lived in Wellington a decade and never seen flooding so bad.
The capital's central library on Victoria St also offered a place to stay for people stuck in the city.
At 6pm, Library staff had started preparing coffee and tea for guests in the mezzanine.
Mayor Celia Wade-Brown said parking officers would only ticket clearways and safety related offences for the rest of the day.Wellington Electricity said some customers would remain without power overnight.
Some homes in the Takapu Valley area east of Tawa and the Ohariu Valley to the west were without power at 4pm.
"We've seen some poles taken out in the rural areas by floodwater so that's why those customers will remain off overnight," a Wellington Electricity spokesman said.
Police deployed specialist teams and off-duty staff to the Kapiti, Porirua and Hutt Valley areas and were preparing for further rain as a high tide loomed.
The biggest downpours were expected in the Tararua and Ruahine ranges overnight.
Stream flows were expected to slow down overnight but bigger rivers could keep rising for hours as rain ran off from watersheds, WeatherWatch forecasters said this evening.
Conditions were expected to be unsettled tomorrow, but not as wet as today, WeatherWatch predicted.
One elderly man dead
An elderly man has died in today's flooding in Wellington.
Police said the body of the 80-year-old man was found near a car submerged in water, with its keys in the ignition, in the Lower Hutt suburb of Petone.
The man was found late this afternoon, hours after the car was found near Sladden Park, Bracken St.
Police said officers searched the area and found the man's body in flooded water near his vehicle.
There were no suspicious circumstances relating to his death.
Police were working to notify next of kin and the death had been referred to the coroner.
Meanwhile, police said all motorists should take extra care and expect delays as conditions were "still treacherous with extensive flooding in many areas" around Wellington.
Man rescued from muddy banks
A man had to be rescued from the muddy banks of the Waikanae River on the bucket of a digger, Kapiti mayor Ross Church said.
The man had been trapped in mud beside the significantly flooded river, he said, and police coordinated the rescue with the help of a digger.
"That's one of the messages we're trying to get out is people please stay away from the water, the rivers and the mud because there's a lot of serious flooding," Mr Church said.
"The last thing we need is people going to have a look and putting themselves and the emergency services in danger."
Future outlook
Surging streams will slow down overnight but bigger Wellington rivers could keep rising for hours as rain runs off from hills, WeatherWatch forecasters said this evening.
Conditions were expected to be unsettled tomorrow, but not as wet as today, as WeatherWatch predicted showers and cooler southerly winds to pick up in the afternoon and evening.
The forecasters expected "strong to gale force southerlies and a few showers" on Saturday, easing by the evening.
WeatherWatch forecast a few early showers in the capital on Sunday but an otherwise dry day.
Monday would be warmer and drier with northwesterlies lifting the high back up to 18C, WeatherWatch said.
By Wednesday, temperatures should return to normal for mid-May.
