"There was lots of models, lots of data, all indicating extremely strongly that this would be a significant event," Auckland Civil Defence head of emergency management operations Aaron Davis said.
The force of the cyclone which looked to be about to hit the city had the potential to cause "lots of loss of life", and the public needed to be warned, he said.
"They don't come around like this very often."
With wind gusts up to165km/h forecast, damage could have been big.
"When we're talking 165, we know anything over 110 is damaging, 130, really damaging. 160km/h, that's bad. We don't see that very often."
An announcement the Auckland Harbour Bridge could be closed was cause for panic for some residents, but Davis said it was all part of making sure people were as informed as they could be.
If the cyclone had hit as expected, the bridge likely would have had to close.
The storm was "localised" and "just drifted off enough" to miss the city. If it had been on track, the results could have been disastrous.
"One of the key things for me is everyone's held together very well, heeded very serious warnings, they've taken actions . . . these are the things that will save life."
Meanwhile, Aucklanders weren't afraid to have a bit of fun on social media after escaping the brunt of the storm.
Posts with the hash tag #CycloneCook were accompanied by wry comment about the anti-climactic nature of the storm.
