Weather Watch warns ex-Cyclone Trevor might drift east from Australia and join forces with a cold front in the Tasman Sea, sparking a "new rain-maker" next week.
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"Next week the remnants of Cyclone Trevor team up with another front to bring maybe the best chance yet at rain into northern New Zealand - one to watch," forecaster Philip Duncan says.
The South Island is currently being slammed by heavy rain and strong winds.
The West Coast region has been hit by 700mm of rain in just 24 hours, causing widespread damage to roads and destroying the Waiho River Bridge.
Weather Watch say this rain is likely to fall apart as it moves into the North Island on Wednesday and Thursday.
"It's unlikely to deliver enough rain to help seriously reverse the big dry - although some rain will be very welcome," Weather Watch says.
"But this secondary burst of rain connected with Trevor early next week may perhaps bring better chances of North Island rain."
More than 500mm of rain has fallen in Westland fell in the last 24 hours and it's still pelting down. Rivers all along the south West Coast have risen to alarming levels, and are dangerously close to bursting their banks.
A State of Emergency has been declared in the Westland District Council area, which runs roughly from Hokitika South to Haast.