A severe weather watch has been put in place for the Bay of Plenty.
Between 20 to 40mm of rain could accumulate today in the Bay, Northland, Auckland, Waikato, Waitomo and the Coromandel Peninsula.
A weather front was expected to move eastward across New Zealand today, a written statement from the MetService read.
"This front will bring a brief period of rain to many areas, especially to those in the north and west of the country."
There was also a risk of thunderstorms with the frontal rain band and possible rainfall of between 40mm to 60mm.
In most areas the rain should ease late afternoon or evening today, but in eastern Bay of Plenty the rain could continue into the early hours of Monday.
The amount of rain could exacerbate the already saturated conditions in these areas, causing rivers and streams to rise further, with possible surface flooding and slips.
People were advised to keep up to date with forecasts in case any areas in this watch needed to be included in a warning.