Up to 60 properties in the Redcliffs area are being evacuated because of concerns about the stability of a cliff face.
Residents in Kinsey Tce and Tuawera Tce and at the bottom of Clifton Tce are asked to go past the Sumner Beach surf club and assemble in an area near the Poseidon Cafe.
Police are making direct contact with each affected household.
A geologist is assessing cracks in a nearby cliff that are causing concern.
It is not known how long residents will be out of their homes.
Local resident Frank O'Connor says his family, including his eight- year-old son and his elderly parents, were told to vacate their Clifton Hill home at just after 8am.
The main road into Sumner has been closed from Cave Tce to Nayland St while the stability of a rock-face is assessed.
Strong wind warning
Meanwhile, Mayor Bob Parker has warned that people should prepare for strong winds expected to hit Christchurch on Monday afternoon, and start securing loose material.
Mr Parker says the nor'-westerlies could disturb loose masonry and whip up silt, causing breathing problems.
MetService says the winds could reach gale force on Monday night.