Upper North Island residents prepare for Cyclone Gabrielle, which could be second major weather event in two weeks

Forecasters say the upper North Island could get a month's worth of rainfall in 24 hours.

And if Cyclone Gabrielle directly hits, there will be slips, floods, trees down, and power outages. 

Civil Defence is warning people to prepare enough supplies for three days, with powerful winds expected to cause blackouts. 

It's worrying many in upper North Island who are facing a second possible weather event in two weeks. 

Duncan Verduyn is out digging extra drains in the hope heavy rainfall from Cyclone Gabrielle runs through them and doesn't ruin his property, again.  

"Too unsafe, there's too much water, there's still a lot of water in the ground. Everything is saturated still."

He's nervous because of just how high the water rose on his Kaipara Flats lifestyle block in the massive floods two weeks ago. 

"It touched the bridge. It raised five or six meters," Verduyn said. 

He was hit with more than 100 slips, as well as masses of old logs. And now he's desperate to avoid a repeat. 

But forecasters and Auckland Mayor Wayne Brown now say direct impact from Cyclone Gabrielle is highly likely. 

"It's not looking good," said Brown.

It's expected to hit the upper North Island on Sunday night, with the most severe impact by Monday. 

"There is a significant weather event coming and we need to be doing what we can in these next few days to get prepared," said Auckland Civil Defence deputy controller Rachel Kelleher.

That means urgently removing anything piled on your kerbsides from the floods and collecting supplies. 

You need to have enough food stockpiled for at least three days, as well as toilet paper and water.

Next on your list should be batteries, a torch and a radio. Emergency experts recommend having a go bag packed with clothes, shoes a raincoat and a phone charger. 

NIWA meteorologist Ben Noll said there could be up to 300 millimetres of rain for the upper North Island in 24 hours - that's 50 millimetres more than the deluge that caused Auckland's floods.

"We could be looking at a month's worth of rainfall in one day. And that's following a month of January where we saw six months' worth of rain in Auckland."

Slip-hit Coromandel has already extended its state of emergency, and Auckland is preparing to open more evacuation centres.

"This time we've had the opportunity to double-check everything beforehand. We've double-checked everyone's got the right phone numbers and contacts and we're taking it dead serious," Brown said. 

Wairau Valley was one of the worst-flooded areas two weeks ago and shoppers there were already stocking up on Thursday. 

"We've got enough food to last, enough beer to last," one shopper said.

"Oh, just a couple of dozen," they added. 

"We were hit quite badly the first time, so we've actually got extra sandbags and all sorts set up."

Everyone hopes the upper North Island can still avoid the worst of it, but after last time, no one's taking chances.