A state of emergency is also in place across the West Coast.
Buller River was expected to peak in the early hours of this morning and Civil Defence controller Douglas Marshall says the full impact of the rain is yet to be felt.
Some streets are flooding because stormwater cannot drain into the Orowaiti River, which is also running high.
Staff have been out all night monitoring the situation.
Reporter Niva Chittock spoke to Susie Ferguson from Forbes Street, where people were asked to evacuate.
