WeatherWatch said the conditions were volatile and the heaviest downpours were continually changing shape and size - which meant not all suburbs would be exposed, and many may just have a few regular downpours.
"You can thank the humid sub-tropical northerly wind flow today for these incoming downpours," the forecaster said.
Earlier today, flights were delayed or cancelled in and out of Wellington Airport as strong gusts of up to 130km/h battered the capital.
Air New Zealand flights to or from Palmerston North, Dunedin, Auckland, Hamilton, Christchurch, Queenstown, Tauranga and New Plymouth were among those affected.
The capital's blustery day came after strong winds blasted parts of the South Island overnight, with gusts of up to 179km/h in Southland.
The Fire Service was called to 19 weather-related incidents overnight - which included roofing coming loose, powerlines arcing and falling down and fallen trees.
Milford Rd was closed due to storm damage.