It's officially the first day of summer, and while Wellington continues to take a battering, warmer than average temperatures appear to be on the way.

Gales and rain continue to lash Wellington after severe weather over the weekend left 15 homes uninhabitable in Plimmerton and caused roads to be flooded and shut.

Niwa meteorologist Chris Brandolino told Morning Report warmer than average temperatures is forecast for all of New Zealand in its three-month outlook for summer.

Some cool spells will come through but that is not expected to define the season.

"In fact November has been a very warm month, apart from Wellington," Brandolino said.

La Niña will drive more northeasterly winds than usual and trigger higher than usual ocean temperatures.

"You're really loading the dice for warmer than average air temperature for the three-month period," Brandolino said.

"The northeast wind - that's coming from a warm place, the subtropics, the tropics. Not only does that carry warmth, but it carries moisture so we think as the summer season matures, as we get to the end of December into say the back half of summer, we're going to see an increase of these rainfall events that come from the north and northeast.

"Heavy rainfall events are certainly at an elevated risk so things like flooding events unfortunately like we've seen the past few weeks, may be a more common occurrence during the summer season than usual."