Gayle Dean said there was a steady downfall throughout the night, recording 30mm by 7.30am yesterday morning.
Meanwhile Civil Defence closely monitored the developing storm throughout the North Island, which threatened widespread flooding.
Yesterday afternoon mayor Craig Little said Wairoa was coping with the heavy downfall.
"Everything's coping as it should do at the moment but I think we're about to meet saturation levels," he said.
"The Civil Defence guys are on top of it, so we're keeping an eye on it at the moment."
Hawke's Bay, Taranaki, Wanganui and the Tararua Ranges were the first to experience the downpour.
MetService warned those areas would experience intense rain for a day and a half.