Surface flooding is an issue in low-lying areas across the city, with the council asking drivers to take care.
The council also warns that earthquake-damaged wastewater systems remain fragile in parts of the city and have been blocked by rain.
"It's possible flooded roads and parks may be contaminated, so avoid the water where possible or make sure you wash your hands and remove and wash any clothing that gets wet," a city council spokesman said.
"Hill roads are currently extremely dangerous for motorists and should be avoided until later this afternoon.
"The weather will remain wet and cold over the weekend. People are asked to check in on older people or those with disabilities who live alone in their neighbourhoods."
