The swells - which may be more than 5 metres - could hang around the Wellington coast until 8pm tonight.
The mountainous seas out of Cook Strait of up to 4.5m high were projected to hit between Baring Head to Sinclair Head overnight.
The Wellington Region Emergency Management Office is urging residents on the coast to have an up-to-date household plan.
A strong wind watch was in place in the Wellington region yesterday as northwest winds approached severe gales in exposed places at times.
Motorists were also being warned to take care on the region's highways with the high winds expected to be hazardous.
Strong southerly winds are however set to ease this evening in the capital.
Yesterday, fierce winds in southernmost districts toppled trees on to powerlines leaving settlements without power.
Damaging gusts up to 120km/h were forecast in Dunedin yesterday and a frightening 130km/h in exposed parts of South Otago until yesterday evening.
Powernet said electricity was out in Dacre and Woodlands due to falling trees. It was also investigating a number of other outages across the region.