“If you live in or near this area, please be prepared to leave immediately if advised to do so. If you feel unsafe, do not wait. Move to higher ground, stay with family or friends, or head to the Wairoa War Memorial Hall, which is open as an evacuation centre.”
People are also advised to avoid travelling through flooded roads.
Following discussions with its flood modellers on Thursday evening, the council said there are increasing concerns that river levels may rise significantly overnight.
At this time, its concern is for the lower catchment of the Wairoa River.
“While the Wairoa River mouth is open, outgoing water and rising flow is competing against large 3m-4m swells coming in from the coast,” it said.
“More water is also expected to flow into the Wairoa River from the upper catchments, with further heavy rain forecast overnight.”
High tide was expected around 12.47am on Friday, with intense periods of rain between now and 3am.
The council is encouraging people who lived in a low-lying area to prepare now, as conditions may change quickly.
“Have essential items ready, know where you will go if you need to leave, and be ready to move quickly if conditions change.
“If you are concerned about your safety, please don’t wait.
“Move now to higher ground or stay with family or friends in a safe location.”
Wairoa Mayor Craig Little said the emergency operations centre has been stood up and will be monitoring the situation through the night.
Around 7.30pm on Friday, the Wairoa War Memorial Hall was opened as an evacuation centre for those in low-lying areas concerned about rising river levels.
Meanwhile, more than 700 properties are without power.
The council said Firstlight Network crews were working to restore power as safely and as quickly as conditions allow.
With heavy rain continuing, the council was urging people to extra care on the roads and avoid unnecessary travel where possible.