Some parts of the Western Bay could get up to 150mm of rain today, forecasters say.
Niwa principal scientist in forecasting Chris Brandolino said heavy rain was forecast as the remnants of Cyclone Debbie passed over New Zealand, siphoning warm wet weather from the tropics with it.
"It makes it a very rich, moisture-laden atmosphere which will produce heavy rainfall," he told the Bay of Plenty Times.
There was some variability in total rainfall, but most areas could expect between 50 to 100mm with others getting localised downpours of up to 150mm between 6am and 9pm today, he said.
April would only normally get 120mm of rain for the whole month.