NZTA said SH2 Petone to Melling has been closed because of flooding.
Drivers going to Wairarapa can access the Rimutaka Hill Road via SH1 and SH58.
Updates can be found at www.getprepared.org.nz
This morning slips closed SH1 between Paekakariki and Pukerua Bay.
A northbound lane was later opened, however there were considerable delays.
There was also flooding south of Waikanae.
Acting District Commander Paul Basham said Paekakariki Hill Road was also closed by flooding as slips, making detour options unavailable.
As the rain was expected to continue throughout today and tonight, drivers should delay travel indefinitely and particularly avoid the alternative routes through the Wairarapa which may become overloaded.
"Our priority is making sure motorists are able to reach their destinations safely," Mr Basham said.
"With the current road conditions and closures, we want to deter drivers from entering the city.
"It is also timely to remind other motorists to watch their speed and drive to the conditions."
While the northbound lane on the Centennial Highway had been cleared, the southbound lane into the city was expected to remain closed throughout the day.
Widespread flooding in the Kapiti district has caused rivers and streams to rise and some residents have been evacuated from homes in Moa and Tui roads in Raumati, Kapiti Council said on its Facebook page.
Eighteen Kapiti Coast residents have been evacuated from their homes.
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Additional reporting by NZ Herald.