All flights into Auckland Airport are being diverted because of debris on the main runway caused by strong winds.
The airport said flights were either being returned to their originating airport or Christchurch.
There is no estimated time for when the runway will reopen, it said.
MetService said the winds have eased but would remain strong overnight in Auckland, Coromandel and Waikato.
Civil Defence said it was not activating or mobilising but were standing by to monitor the response.