Torrential rain from early evening flooded areas across the city, and the Heathcote and Avon rivers have flooded across neighbouring roads.
A spokesperson for Fire and Emergency said people have been evacuated from the Le Bons Bay area on Banks Peninsula.
The rain has closed some roads, prompted slip warnings and wastewater overflows have contaminated floodwater. All floodwater should be considered contaminated.
"The Heathcote and the Avon rivers have flooded across roads in places, and we've got a bit of surface ponding from these heavier falls from earlier in the evening ... There are multiple road closures across the city. But it's spread out across the flatland across the city rather than in any one place," Beaumont said.
However, some areas have been hit worse than others.
The rain had moved south of the city by late Wednesday, but caution should be exercised, she said.
Christchurch City Council said rain had eased and council contractors would be out at first light to assess damage.
In Selwyn, a water conservation notice has been issued for Springfield residents.
The Selwyn District Council said that was due to cloudy water from heavy rain and low reservoir levels.