MetService has issued a heavy rain warning from 4am today to 3am Friday for the Bay of Plenty, west of Edgecumbe, where between 120 - 170 millimetres of rain was forecast.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible.
A heavy rain watch is also in place for Bay of Plenty areas east of Edgecumbe, Taupō and the Coromandel Peninsula.
More than 200 homes have been evacuated and a state of emergency declared in Nelson as a severe "atmospheric river" rain and flooding event hits the South Island.
Atmospheric rivers are large and extremely high plumes of moisture that move in the atmosphere from the tropics to the mid-latitudes, where New Zealand is located.
University of Otago senior lecturer in geography Dr Daniel Kingston said although this specific weather event had not been analysed regarding the influence of climate change, it was "more than likely playing a role".
Average air temperature had warmed by slightly more than 1C over the past century, and as the atmosphere warmed it could hold more moisture, increasing the likelihood for extreme heavy-rainfall events such as this.
"Sea surface temperatures around New Zealand are also warmer than average right now, which can further amplify these sort of events."
Kingston said this event could be more damaging because it comes on top of an already exceptionally wet winter.
This July was the wettest on record, while more than 40 locations have experienced record or near-record rainfall, he said.
"The ground is already very wet, with limited capacity to absorb further rain."
