Heavy rain has led to levels rising in two rivers in the Nelson-Tasman region and locals have been alerted by phone on Tuesday night.
Nelson and Tasman Civil Defence manager Roger Ball says much of the rainfall has fed into the Aorere River and the initial alarm level has been triggered on it and the Anatoki River.
It is too early to know how high the rivers could rise, but locals have been contacted as a precaution.
On 28 December last year, the Aorere reached its highest level in 150 years, triggering some damaging flooding.
West Coast river bursts banks
Police are keeping a close watch on flooding at Fox River on the West Coast after it burst its banks on Tuesday.
Heavy rain has been falling in the region and while no houses have been flooded, police have helped property owners to collect their belongings as a precaution.
More rain is expected overnight on Tuesday and police will monitor the situation at the settlement.
State Highway 6 between Greymouth and Westport is affected by flooding and motorists are advised to avoid the 100km stretch of road if possible.
Buller District Council says its Civil Defence team has not been alerted.