Heavy rain originally forecast to pummel Northland and Auckland overnight is now expected to hit Wednesday morning.
On Tuesday, MetService upgraded a heavy rain alert for Northland from a watch to a warning.
Many other regions have rain and wind watches in place.
Civil Defence Northland warned holidaymakers that the rain could cause streams and rivers to rise rapidly as well as surface flooding and slips, which may impact driving conditions and lead to road closures.
“The strong winds may also add to these potential hazards, as strong wind gusts can damage trees, powerlines, unsecured structures, and temporary structures such as tents,” a Facebook post said.
Boaties were warned a heavy swell was expected along eastern coastlines from Northland to Coromandel Peninsula.
The heavy rain warning is in place for Northland until 7am on Thursday with between 110 and 160mm of rain expected to fall.
Between 7am and 9am Wednesday, 5.1mm of rain is expected to fall in the top of the North Island.
A heavy rain watch, a downgraded threat level from a heavy rain warning, is also in place until Auckland and Coromandel.
In Auckland, the warning is in place until 9am on Thursday and in Coromandel it’s in place until 9pm on Thursday.