Wellington's south coast residents are bracing for huge waves similar to those which have previously smashed windows and inundated their homes with water.
Mayor Andy Foster has declared a local state of emergency with the potential for eight-metre-high swells this evening.
Breaker Bay residents have been told to evacuate by 6pm, before the situation turns dangerous for residents and emergency services.
Affected properties are those on Breaker Bay Rd between numbers 53 and 194.
Cordons are in place at the northern and southern entrances to Breaker Bay and are under guard by council contractors.
No one, including residents, is being allowed in.
Foster told Newstalk ZB's Heather du Plessis-Allan the sea was "pretty wild" this morning with the swell at about 5.5m.
But his main concern was later on tonight at 9pm when waves will be at their strongest.
Waves as high as 1.5m could hit houses, he said.
Breaker Bay resident Heidi Barrenger was driving one of her daughters to gymnastics when her cellphone lit up with messages asking if she was okay and talk of evacuation.
"We quickly turned our car around and as a family decided that we definitely needed to evacuate so we packed our bags."
The family is staying with friends in Seatoun for the night.
Barrenger said she felt panicked.
"But we've been living in Breaker Bay for about 12 years now and we've had this happen a couple of times. We've only evacuated one time before from an earthquake and tsunami risk but we've had storms before."
Her daughters were excited to begin with, she said.
"I think probably they picked up on a bit of panic from us and then they started being a little bit more scared and anxious about how long we were going for and if the house was going to be okay."
Barrenger "cracked open a bottle of red" when she was safely in Seatoun.
"We will just all try and be calm and not think about what's going on out there."
Craig Boyes, another Breaker Bay resident, said he and his wife and the family dog were staying the night at their daughter's house in Wadestown.
"I'm pretty relaxed about what we might come back to. We've had a number of storms there before and it's not uncommon to get the odd log or big rocks come across the road."
Meanwhile, Owhiro Bay resident Kristen Meads told the Herald she has put sandbags across all four doors to her house, including the cat flap.
She has removed all the pots from her front yard and stacked her outdoor furniture so it can't be moved around in any water.
Her treasured succulents are on top of the woodshed.
The Wellington Region Emergency Management Office (WREMO) has advised swells will be at their heaviest at 9pm tonight.
Meads said she felt more prepared for the storm this time compared to when huge waves struck in April last year, when she had no warning.
"I was standing at the kitchen counter looking out when the wave actually hit, it went over the house and it went all around the side of the house."
Water then came gushing through under the doors.
"Our garage door was basically like a pretzel inside of the garage, the force of the water was just insane", Meads said.
"You can never know what water's going to do, it's really powerful.
"Our friends' window was smashed in last time and that would be my biggest fear I think."
Meads said she was watching Friends tonight to pass the time.
An emergency mobile alert has been sent out advising of those affected by the evacuation, for people to take their pets with them, to stay out of the water, and avoid walking near shorelines.
High risk areas include Owhiro, Island, Houghton, Lyall, Reef, Flax, Eve, Karaka and Breaker Bays, Moa Point, and Seatoun.
People within these areas should prepare a 24-hour grab bag with supplies in case they have to leave at short notice.
Large waves are expected in the inner harbour area, Petone and Eastbourne, but they are not forecast to be as big as those on the south coast.