Residents along parts of Wellington's south coast are being told to prepare in case they need to evacuate their homes tonight.
Wild weather is lashing the area, with gusts of up to 100km/h and 6m swells expected overnight.
The strongest winds are expected to coincide with the next high tide at half past one in the morning.
Wellington City Council says residents of Owhiro Bay - where properties were damaged and homes evacuated during huge swells in April - need to be ready to safely leave their homes if the weather gets bad enough.
It said it has cleanup crews on standby if necessary, and it was asking people not to put out recycling this evening and to tie down trampolines.
MetService meteorologist Kyle Lee said the worst of the southerlies would hit from 6pm and peak around midnight.
"Because of the strong southerly surge we are also expecting combined waves and swells to get up to five-and-a-half, maybe even six-and-a-half, metres for the south coast this evening in Wellington - unfortunate timing in terms of maximum swell and combined waves."
Some Owhiro Bay residents were boarding up their windows and moving their vehicles early this evening in preparation.
Isaac Shanley - who's house is still being repaired after the April storm - said he has lifted electronic items off the floor in case the property gets flooded again.
He said it was an anxious time.
"We're going to stay here as long as we see that it is okay, if not we'll probably [leave and] go to different houses."
But Doug Van Boheemen, who has lived in Owhiro Bay for a decade, said weather like this happened at least once a winter and he did not expect there to be much damage.
Interislander cancelled four sailings today and two early morning crossings tomorrow.
The height of the bar indicates the strength of the wind ️— NIWA Weather (@NiwaWeather) June 30, 2020
Wellington and the eastern South Island will certainly 'raise the bar' on Wednesday-Wednesday night!
50 km/h pic.twitter.com/ehVTfqtNpL
Interislander executive general manager Walter Rushbrook said all affected passengers would be contacted and transferred to alternative sailings. He said the company regretted the inconvenience to passengers but safety had to be its top priority.
Bluebridge has not announced any cancellations.
Warnings for severe gale southerlies are in place for Wellington, southern Wairarapa, northern Hawke's Bay and Gisborne.
Coastal areas of northern Wairarapa and coastal Hawke's Bay south of Cape Kidnappers could also get severe gales.
Gisborne and Hawke's Bay are expected to get about 5m swells by the afternoon tomorrow.
Heavy snow warnings have been issued by MetService for Taihape, the Ruahine Range and the Tararua Range, while a heavy snow watch has been issued for the ranges of Marlborough.
The Desert Road (SH1) could get snow up to 25cm deep at higher altitudes, while the Remutaka Hill Road (SH2), the Napier-Taupo Road (SH5) and Lewis Pass (SH7) will have rain turning to sleet and snow from this afternoon.
Temperatures are expected to be low through to Friday.
This morning, Taupō and Blenheim were sub-zero, both still at -1C by 7am, and colder than Queenstown at 4C, while Auckland and Wellington were 7C.
Cold southerlies cover the country this working week with temperatures expected to remain on the wintry side. Here are your observed temperatures across the main centres this morning. Nothing into the double digits and a few stations still in the negatives. ^KL pic.twitter.com/PINETvErBQ— MetService (@MetService) June 30, 2020