MetService warned that in the 36 hours from 3am Thursday to 3pm Friday, between 150mm to 180mm of rain could accumulate, particularly about the eastern ranges. MetService predicted the rainfall would peak about 6am tomorrow morning, with 27.9mm of rain expected to fall about that time.
Read more: Tauranga downpour: how much fell over night
The wild weather has been causing havoc in other parts of New Zealand. In Nelson, Mount Maunganui College old boy Aaron Lyttle helped in the rescue of a woman and her 9-month-old baby after they became stranded in floodwaters on Wednesday night.
The woman, her husband, baby and another man became trapped in their vehicle when a flash-flood caught them out on a road near Waimea River, 20km southwest of Nelson.
The Mount man and Nelson surf lifesaver, along with club president Marcus Gardner, came to their rescue amid the growing darkness.
Mr Lyttle said he and Mr Gardner made it to the car in an inflatable rescue boat, floating over farms and cutting through several fences. He said they had their "minds on the job" and were not scared despite the stormy weather and growing darkness.
They got the people into the boat and kitted them out with lifejackets, tucking the baby into her mother's jacket, and navigated back to safety, where police and ambulance services comforted and warmed them up.
Mr Lyttle began surfing when he lived in the Mount and attended Mount Maunganui College 30 years ago.
