Several homes in Plimmerton, Porirua, have been evacuated after heavy rain hit the region, closing the main road out of Wellington.
Porirua Mayor Anita Baker said work was under way to pump water out of the buildings.
An "initial welfare point" had been set up at the fire station for residents needing help, and a shuttle van was available from Moana Lodge to pick people up.
The New Zealand Transport Agency (NZTA) earlier warned motorists to delay their travel after State Highway 1 was completely closed off by floodwaters between Plimmerton and Paekakariki.
Lanes are now open in both directions, but only one lane is open northbound. Traffic remained backed up and motorists were asked to stay off the roads if possible.
Pictures from NZTA's traffic cameras show the flooding around the Plimmerton roundabout has almost receded as of 2pm.
Hazel Kale's driveway filled up with floodwater. Photo / Supplied
Paekakariki Hill Rd and Grays Rd remained closed.
Members of the public took to the NZTA Twitter page on Sunday morning to warn about slow-moving traffic caused by the flooding.
"Sitting just before Paekakariki southbound, only edging forward. People turning round," one woman said.
Another person said they hadn't moved in 10 minutes.
The region was hit by steady, heavy rain overnight and through much of the morning.
An NZTA spokeswoman said around 11.30am floodwaters appeared to be receding as the rain had stopped.
By midday, Fire and Emergency NZ had received about 20 calls in relation to flooding in the Plimmerton area.
A spokesman said it was general assistance calls - "flooding on the property, flooding outside".
He said Fenz responded to 16 calls and handed six over to the local council and police.
He said Plimmerton was "a small community, so a lot of people are coming to the fire station to report their calls as well".
Hazel Kale has some cleaning up to do after floodwater poured into her living room. Photo / Supplied
A command unit had been set up and localised resources were being dispatched.
Metservice meteorologist Andy Best said there had been a "dramatic" amount of rainfall in the area, particularly on the Kapiti Coast.
"Places like Levin, in just six hours, have seen around 40mm of rain."
Paraparaumu had 45mm and Waikanae had 59mm of rain in the six hours to 11am, Best said.
But there was good news: "the southerlies which brought that ... have actually started to clear".
Best said Wellington City was currently dry and that would continue up the coast.
"So we are seeing a vast improvement in conditions this afternoon and into the evening.
"The winds will all die out and give the opportunity for places affected by this rain to dry out."
However, Best said the weather radar had "quite another dramatic feature" coming up the country tomorrow.
He said there could be "very strong, possibly severe, gales", southerly winds and rain for the lower part of the North Island and the Marlborough Sounds.
"A very cold southerly change comes up tomorrow evening and it will be quite dramatic as it moves through the capital."
One woman who lived on Airlie Rd said some of the houses backing onto Karehana Park were badly flooded, but hers had escaped the worst of it.
Her yard was flooded and the water was "not moving" due to blockages in the drainage systems in the street, but thankfully the water had not gone into her home.
Hazel Kale said the water flooded part of her living room.
She had never seen the area flood so badly in the time she has been living there, and said some of her neighbours who had lived there for 40 years told her it had never been so bad.
"The garage always floods when it rains pretty badly," she said.
She prepared her house for the rain then left to check on her parents, but when she came back the flooding was worse than she had expected.
"The water just started flowing straight down the driveway and it got quite high. It started coming into the lower parts of my house."
The water has all drained away now, but looked "impressive" at the time.
"It was probably more a shock than anything," she said.
Another nearby resident said their house was raised off the ground, so the water came underneath but did not enter the building.
It had drained away now and left a lot of mud, he said.
- With Jake McKee Cagney