The heavy rain warning for Bay of Plenty has been extended to Hawke's Bay.
The MetService says the deepening low bringing up to 90mm of rain to Bay of Plenty and Rotorua on Wednesday is moving southeast across the North Island.
From evening until about midday on Thursday the Hawke's Bay south of Napier can also expect a deluge, and up to 100mm may fall, especially around the hills.
"People are advised that this amount of rain can cause rivers and streams to rise rapidly, with slips and surface flooding possible," the MetService said.
Civil Defence teams are bracing themselves for slips and surface flooding on Wednesday afternoon.
Drivers are being urged to take extra care on the roads in the difficult conditions. Heavy rain caused major issues for road users last week.