Waka Kotahi NZ Transport Agency warns the Auckland Harbour Bridge could close on Monday due to the threat of strong wind gusts.
Strong wind watches cover much of the upper South Island and North Island tomorrow afternoon, and MetService warns west to southwest winds may approach severe gale strength in exposed places.
Waka Kotahi says an amber alert is in place on Monday morning from 4am - 7am with wind gusts of 75 - 80km/h forecast. Under an amber alert, speeds are reduced and some lanes on the bridge may close.
And a red alert is in place from midday - 9pm with wind gusts of 90 - 100km/h forecast, and the possibility of gusts up to 110km/h. Under a red alert, all lanes on the bridge are closed.
Accordingly, the bridge will remain in a 4x4 lane formation throughout the day and Waka Kotahi warns it will reduce speeds, close lanes or close the bridge if necessary.
"Motorists are urged to drive to the conditions, look out for the electronic message boards which will indicate lane closures and reduced speeds, or full bridge closure, and stay within their lane while travelling across the bridge," it said in a statement.
"Drivers of high-sided vehicles and motorcyclists are advised to avoid the Auckland Harbour Bridge and use the western ring route on State Highways 16 and 18."
