The Insurance Council predicts the cost of the Nelson flood will be more than $16 million.
Drains and sewers were overwhelmed in the Richmond and Stoke areas on Sunday when 100mm of rain fell in one hour.
The Insurance Council has received 1300 claims from property owners and preliminary reports reveal there will be more claims than after the Nelson flood of 2011.
Chief executive Tim Grafton said the costs will also be higher as the recent flood affected more businesses than in 2011.
Mr Grafton said 1000 property owners in the Bay of Plenty region have also claimed for insurance due to heavy rain.
Meanwhile, wet weather has moved away from the Richmond and Stoke areas in Nelson, allowing a start to the clean-up.
The region received only 12mm of rain overnight on Monday.
On Sunday, 100mm fell in just one hour, overwhelming drains and sewers and flooding properties.