Northlanders are being warned to brace for a storm wilder than any they have seen in many months.
MetService is predicting a long period of heavy rain and gale force winds as a deepening subtropical low starts moving over the top of the country on Wednesday night.
Forecaster Gerard Bellam said last week's drought-breaking rain, though heavy, was delivered by a "common or garden" front, without the powerful easterly winds expected in coming days.
MetService's earlier heavy rain watch has been upgraded to an orange heavy rain warning, which took effect from 3am Wednesday and would last until 8pm Thursday.
That was coupled with an orange strong wind warning from 3pm Wednesday to 8pm Thursday.
Bellam said the winds were expected to reach 120kmh with damaging gusts of up to 140kmh possible, enough to bring down trees and power lines, and blow away unsecured objects such as trampolines.
"We haven't seen wind like this for quite a while in Northland - and it's coming in from the east, a direction that may cause trouble for some structures and trees that aren't used to it," he said.
Bellam described it as a "slow-burning storm", largely because a high pressure system parked southeast of the South Island would slow the low's normal southward progression.
Rain was likely to continue until Saturday in Northland, he said.
He advised checking drains and gutter before the rain hit in case they were clogged with autumn leaves.
Bellam said there was a moderate chance of Northland's orange strong wind warning being upgraded to red, but only a low chance of an upgrade of the orange heavy rain warning.
A strong wind warning was also in place for Auckland and Great Barrier Island from 9pm Wednesday through to midnight Thursday.
After Northland the wild weather would make its way slowly down the country, with heavy rain watches so far in place for Auckland, Great Barrier Island, Coromandel Peninsula and Bay of Plenty; and strong wind watches issued for Coromandel Peninsula, Waikato, Waitomo, Taumarunui, Taihape, Taranaki and Buller.
