"There is a lot of uncertainty with regards to the amount of rain that may fall and the exact area affected, but rainfall amounts may reach warning criteria in localised places," MetService said.
MetService meteorologist Tui McInnef said instruments at Whitianga Airport had recorded 51.8mm of rainfall in the 12 hours before 11am while 52.1mm hit Tauranga where rain was strongest between 3am and 11am.
100mm of rainfall fell in the same period east of Tauranga, through Te Puke and a little further inland, McInnef said.
Rotorua saw less rain with 23.2mm recorded in the day so far.
The weather is set to improve on Saturday with a few showers developing on Sunday and through to Anzac Day Monday.
A motorist said there was some surface flooding near Bayfair on the B2B and along Papamoa Beach Rd.
The golf course and driving range opposite Bayfair "has rivers and lakes running through it", he said.
