Surface flooding was also becoming an issue with the New Zealand Transport Agency issuing an area warning between Tangoio to Raupunga along State Highway Two, advising people to drive to the conditions.
They also reported flooding along SH5 between Ellis-Wallace Rd and Waipunga Rd and a temporary speed restriction of 30km had been put in place.
The rain was expected to continue through the night with another 60mm-90mm predicted to fall.
MetService meteorologist Lisa Murray said the heaviest accumulations were expected about the ranges and the coastal hills south of Cape Kidnappers.
"10mm-20mm of rain could fall per hour at its peak."
The warning status will be re-looked at tomorrow morning by MetService and will either be removed or reinstated.