A severe weather warning was in place for Wellington, and the Horowhenua Kapiti Coast.
Heavy northwesterly rain was expected until Saturday morning, MetService said.
Until 9am tomorrow, 150 to 300mm of rain was expected about the ranges and foothills, with 80 to 120mm closer to the Horowhenua Kapiti Coast and in northern parts of Wellington.
A severe weather watch for strong winds was also in place, and Wellingtonians could expect gale northwesterlies, gusting up to 130km/h in exposed places.
The gales were expected to ease early tomorrow morning.
The New Zealand Transport Agency are advising Wellington commuters to plan ahead for their journey home tonight and allow extra time for travel, with the wet weather forecast to get worse around 4pm.
Regional Performance manager Mark Owen said with the rain expected to get heavier later this afternoon the Transport Agency was urging the public to drive to the conditions.
"We are keeping a close eye on the roads and the weather forecasts. Our contractors have cleared all the drains at spots on our highways that are prone to flooding and we're working closely with our transport partners to prepare for and mitigate the impact of the wet weather.
"Slippery roads are much more dangerous, as they can turn minor errors into major problems.
"Heavy rain and wind can also result in debris on the road, so keep your eyes peeled for any obstructions."
State Highway One between Otaki and Levin had already been affected by surface flooding, and the speed limit had been lowered to 30km/h.
Winds were forecast to get stronger particularly on the Rimutaka Hill Road so high-sided vehicles, caravans, campervans and people travelling by bicycle or motorbike were advised to take care, the Transport Agency said.
Two trucks have were blown off the road in high winds near Wellington earlier today.
Police said one truck came off the road between Dannevirke and Woodville. Another truck came off the road south of Pahiatua.
Police asked anyone driving a truck, or high sided vehicles to stay off the road, as winds batter the wider region.