The Far North District Council says the cost of cleaning up this week's floods will be in the millions.
The equivalent of nearly three months of rain fell in Northland between Sunday and Tuesday morning, causing dozens of slips, road closures and damage to farmland.
State Highway 12 north of Dargaville is still impassable on Wednesday.
Up to three months of rainfall fell in a 36-hour period in the Northland region earlier this week.
MetService says on average, about 200 millimetres of rain fell from Sunday evening through to early on Tuesday morning. Touwai Bay, north-east of Kaeo, recorded 370mm.
The council says there is significant damage to infrastructure and estimates the total clean-up costs to be between $3.5 million and $4 million.
Spokesperson Richard Edmondson says about 50 local roads have been damaged and a number of sewage treatment plants flooded.
Mr Edmondson says farmland is still under water and vulnerable to more flooding if there is more heavy rain.
He says these types of weather events are expensive and cites the example of State Highway 10, south of Kaeo, which has been a problem for some time.
The New Zealand Transport Agency had just fixed it and the recent flooding has caused further slips.
The Whangarei District Council says it's cleaning up as well, with contractors out assessing roads.
Meanwhile, MetService says the severe weather warning for the Northland region has been lifted.