A local state of emergency has been declared in the Bay of Plenty, ahead of heavy rain brought by Cyclone Cook on Wednesday.
From midday Wednesday it is expected the region is expected to receive 200 to 250mm of rain.
The region is already dealing with the effects of Cyclone Debbie, which hit the area last week.
The declaration means that there will be a regional co-ordination of Civil Defence Emergency Management preparedness and response.
A weather system over the Tasman Sea is expected to bring heavy rain to the South Island on Tuesday, and the North Island on Wednesday.
The north and west of the South Island, and Otago, will be hammered on Tuesday, with up to 200mm of rain predicted from the early afternoon for 48 hours in most areas, according to the MetService.
Nelson is expected to also get hit by up to 200mm of rain in the 18 hours from 4pm.
From midday on Wednesday, the Bay of Plenty and Taupo could get drenched by 250mm of rain over two days.