Almost 5mm of rain has already fallen in Tauranga this morning but the worst is yet to come with a severe weather warning issued by the Metservice.
As much as 90mm of rain is expected in the Bay of Plenty, Rotorua and Hawkes Bay later today and into tomorrow morning.
A deepening low is expected to move southeastwards across the North Island today and early Thursday, bringing a burst of heavy rain, then away to the east later Thursday.
The heaviest rain was expected in Bay of Plenty and Rotorua, where 90mm of rain could accumulate, also in Hawkes Bay south of Napier from this evening to about midday Thursday, where 100mm may accumulate, especially about the hills.
People are advised that this amount of rain can cause rivers and streams to rise rapidly, with slips and surface flooding possible.