King tides are due to wash up on Auckland's shores just after 10am today, and the New Zealand Transport Agency is warning people to take extra care on coastal roads.
The king tide will last until tomorrow. At its highest, the tide is expected to reach 3.7m, about 60cm higher than normal.
NZTA national journey manager Kathryn Musgrave said areas most at risk from flooding included a section of highway and adjoining cycleway on the Northwestern Motorway causeway between Great North and Rosebank Rds, and the Northern Motorway near the Onewa Rd interchange.
In the city, some parts of Tamaki Drive could also flood.
Ms Musgrave said some traffic might be diverted.