Auckland Mayor Wayne Brown is defending the timing of the city's state of emergency declaration.

It was declared at around 9.30pm - after torrential rain and flooding hit the city from mid-afternoon.  

Earlier in the day, the Mayor was under pressure to make the declaration - including from National Party Leader Chris Luxon and local councillor, Jo Bartley.

“You just have to look online to see the chaos out there. No need to wait. Declare state of emergency,” she said. 

But in a press conference late this evening, Brown was defending his actions. 

"There has been some speculation I could have acted sooner, but I couldn't have. This is a formal process, not to be taken lightly," he said. 

Brown says the declaration has consequences.

"And so I've listened to the professionals in the field. The professionals who've been out there reporting back to their control centre. We have been on standby to receive the correct time for me to sign it, and immediately after I was given that call to make that decision, I did."

Brown says the weather event is "as intense as anything we've seen, but it covered a much wider region than what has happened before".

"I personally I have been involved in one or two in the past, and careful assessment is important, careful steps, not rushed steps," he said. 

"And my role isn't to rush out with buckets. It's to be here ensuring that the centre is well organised and that we are taking the appropriate steps at the appropriate time, not rushing into them today in response to noise outside.

"This is a formal serious business, and the effects of it will go on for some time."

Miserable summer weather hits Auckland on January 27. Photo / Michael Craig

Civil Defence says the scale of the damage is still unclear, and teams will be out at first light to make assessments. 

People who have been evacuated from their homes can go to St Leonards Road School in Kelston where a Civil Defence centre has opened.