Beachgoers are being urged to take care with strong swells expected to hit Whanganui beaches tomorrow morning.
Storm force winds south of Australia in the last week have generated exceptionally powerful waves which are heading to New Zealand.
These large long period waves will arrive on the southwest of the
South Island Wednesday evening and then will sweep up the to the west coast of the North Island on Thursday.
While the swell is only expected to be four metres the swell period will be unusually long at 20 to 22 seconds, producing very large breaking waves inshore.
"Sweeping onshore waves could be a danger to swimmers all along the west coast due to strong inshore currents, undertows and rips associated with this long period swell," MetService Meteorologist Lisa Murray said.