"There is particular concern with the Kaimais. They could get about 150mm and that will affect rivers and streams and everything else that flows down. They will rise rapidly."
Farmers like Rick Powdrell, pictured, have been warned to prepare for flooding as heavy rain is forecast to drench the region.
A severe thunderstorm watch was issued for the Coromandel, northern Waikato and Western Bay of Plenty which would remain in place until 3pm Wednesday.
The heavy rain was expected to ease off by this afternoonbut the wet weather would be back tomorrow .
Niwa forecaster Chris Brandolino said it would not be steady rain from sun up to sundown for five straight days, rather the area could expect the heavy rain to come in waves.
He said it was not exactly clear where would be the hardest hit but by 6pm today some areas of the Bay could receive anywhere from 60 to 80mm of rain.
By Sunday some areas could see an excess of 150ml of rain.
From Thursday until Sunday the bands of heavy rain would continue, though dispersed with some lengthy dry periods.
"The driver of this is a low pressure system out over the Tasman. That's going to loiter, sit and spin from Tuesday to Sunday before moving off east and south. At the same time there is a high pressure system south and east of the low pressure.
The Metservice rain radar as of late last night. Photo/MetService
"The two are going to act like a cog, inducing a flow of air from the tropics and subtropics, bringing humid air to fuel the downpours," Mr Brandolino said.
Mr Brandolino said there was a concern for flooding due to heavy rainfall in such short periods.
Local farmer and Federated Farmers rural security spokesman Rick Powdrell said a follow up to the rainfall a few weeks ago would be appreciated - though he was not looking forward to the high intensity rainfall.
"That last rain we got, a lot of us received 200mm but not high intensity and we coped with it," he said.
The high intensity rain over a short period caused flash flooding, erosion and culverts washing out.
