Civil Defence in Northland says inaccurate weather forecasts before Cyclone Wilma at Anniversary weekend in January, affected the region's emergency response.
Holiday-makers were stranded in flash floods, motorists had to be rescued from deep floodwaters and people were evacuated from damaged homes.
A debriefing paper on the Civil Defence handling of the event says the MetService forecasts gave Civil Defence an overly optimistic view of the likely impact.
Northland Regional Council says the region had almost twice the rain forecast.
Tony Phipps, the officer in charge on the night of the floods, says that by the time extra council personnel and contractors were called out, the roads were flooded and many could not get through to do their jobs.