An unusual weather pattern produced a series of water spouts over Cook Strait on Tuesday afternoon.
Five or six were detected with speeds estimated at 50 to 60 km/h a quarter of the speed of big American tornadoes.
None caused any damage.
MetService forecaster Hordur Thordarson says the Wellington area was caught between a northerly wind and a southerly wind.
He says when that happens the convergence can cause instability and a spinning motion that causes the spouts to form.
Mr Thordarson says he does not expect a recurrence on Wednesday.