Residents on Wellington's south coast are being advised to batten down the hatches in preparation for huge swells tonight.
MetService is warning of heavy swells of up to five meters peaking on Wednesday evening and continuing into Thursday morning.
Meteorologist Peter Little says the waves are being driven by southwest gales coming from the Southern Ocean.
"These large swell waves have the potential to cause coastal inundation and erosion of our shores, especially around high tide."
The South Coast of Wellington is expected to bear the brunt of the severe weather, with residents in places like Owhiro Bay being warned to be cautious.
"Beach users and boaties are advised to exercise caution as these unusually high swell waves will be hazardous," said Little.
The Interislander says it is aware of the bad weather impacting the Cook Strait, and anyone booked on a sailing which could be affected will be told personally.
"KiwiRail monitors the weather situation in Cook Strait closely, and treats safety as its first priority in deciding whether to cancel services.
We keep customers who are directly booked with us informed of any disruptions."
It follows another surge which occurred Sunday night and deposited sand and debris across the beaches, burying some stormwater drains.
A statement from Wellington Water said the outlets would not be physically cleared until after Wednesday's surge due to safety concerns.
"In the meantime, the team will be auditing the stormwater outlets at the 34 locations between Owhiro Bay and Seatoun to determine the extent of clearance works required for each site."
Sunday evening's swells also closed Moa Point Road through until Monday morning after rocks and debris were strewn across it by the waves.