Earlier Wellington Water was advising motorists to expect delays on SH1 at Paremata due to a burst wastewater main between the Aotea turnoff and Plimmerton, 200 metres north of Aotea lagoon.
The incident had caused a wastewater manhole to overflow sewage on to Station Rd and Paramata Cres.
The public were asked to avoid swimming in Porirua harbour for the next 48 hours, and residents of Featherston and Greytown are asked to conserve water until further notice.
Wellington Water was called to the burst wastewater main at around 8am today, said customer planning manager Sam Lister.
"This has caused wastewater to overflow across SH1 and into the Paremata harbour. State Highway 1 is currently down to one lane northbound and people should expect delays.
"There are nine wastewater tanker trucks on-site helping to reduce the overflow on SH1 and crews are planning to do an urgent repair."
Works were expected to go into the late evening tonight, and Lister warned there could be more burst pipes.
"With the heavy rainfall likely to cause more overflows, we're also asking residents in Whitby, Paremata, Plimmerton, Pukerua Bay and in the northern parts of Aotea to minimise water use as much as possible.
Strong winds reaching 130km/h in some places are cancelling flights at Wellington Airport and blowing roofs off houses, as flooding and debris is reported across the region.
Slips and flooding have also closed SH2 between Upper Hutt and Featherston.
The wild weather that has battered the South Island's West Coast is sweeping up the country today - with most parts of the North Island in for periods of heavy, intense rain and high wind.
Wellington Airport said the gusts had caused flight disruptions all day.
A spokesperson said 26 Air NZ departures and 28 arrivals to Wellington Airport had been cancelled on Saturday, as well as all Sounds Air flights.
Wellington City Council urged motorists to take special care on the city's roads as heavy rain and strong winds hit the region.
They had received more than 60 calls to reports of flooding on roads and into private properties since 8am today.
Crews were attending a tree down in Oban St, Wadestown, and there had been multiple reports of flooding – including into shops in Adelaide Rd, Berhampore.
MetService meteorologist Rob Kerr said strong winds were expected to continue through the rest of the day, with a weather warning in force until 6pm.
Severe north to northwest gales could gust to 140km/h in exposed places.
The wind gauge on Wellington's Mt Kaukau recorded peak gusts of 130km/h or more between 8pm last night and 1am this morning.
Kerr said the weather would move up the country today swiftly - bringing periods of heavy rain to much of the North Island.
"Bang, it's going to accelerate right across [the North Island]. It will be quite brief moving through," he said.
The region remained under a heavy rain watch, with Kelburn recording 31mm over a six-hour period and 32mm at Trentham.
"The heavy rain watch goes through until 4pm this afternoon and it's followed then by some showers and northwesterlies right through for the rest of the day and through tomorrow.
"The heavy wind watch goes through until 3am tomorrow morning."
There was also a travel warning for people heading north on SH1, with large waves expected in northwestern parts of the region, such as the Kāpiti Coast and Pukerua Bay.
"With high tide at around 3pm this afternoon we could see some spray and debris affecting SH1 north heading out of the city, north of Pukerua Bay," Kerr said.
He said NZTA would also be keeping an eye on the road.
Earlier this morning the conditions had downed a power or phone line on Northland Tunnel Rd, caused a tree to fall on to Ohiro Rd and contributed to a vehicle accident.
Police had been receiving weather-related calls in Wellington since 5.45am, a spokeswoman said.
"Flooding on SH1 at Papakowhai ... appears to have contributed to a vehicle spinning out at 8.20am. No injuries and the vehicle has been towed," the spokeswoman said.
There was also flooding on Hutt Rd at Kaiwharawhara and Grays Rd in Plimmerton.
There had been three vehicles involved in a crash on the Hutt Road at 11.50am with no injuries reported.
Slips had also been reported in the southbound lane of SH1 near Newlands, on Hudson St, Island Bay, and at Tai Paku Paku Rd, Karaka Bays.
Council had also advised of flooding on Waikowhai St, Ngaio at 11am.
Fire and Emergency had 28 weather-related calls overnight and responded to 19 in Wellington.
A spokesperson said the callouts had included roofs lifting, windows being blown in and fallen trees.
"This morning we continue to respond to a steady stream of calls for assistance, including surface flooding, trees bringing down power lines and storm damage to properties. Our crews are working with power companies where power lines are involved."
Shift manager Belinda Beets said a large section of a roof came off a house in Newtown.
Roofing iron and a sign also came loose elsewhere in that suburb.
Steel was hanging from a roof on an apartment block on Taranaki St in the CBD, and doors were blown out in Ngaio.
