The storm has now hit North Canterbury.
Emergency services say there are numerous reports of flooding.
Police say the worst affected areas include Amberley, Leithfield and Rangiora.
At Sefton, 12 residents were evacuated to the local school hall.
Roads around the Waimakariri river are also all flooded, along with some roads in central Christchurch.
Civil Defence says river levels in the region are high.
State Highway One is closed between Saltwater Creek near Sefton and Waipara, and between Kaikoura and Blenheim.
State of emergency
Civil Defence says a state of emergency will remain in place for the Marlborough region until at least Thursday afternoon.
An emergency was declared by the Marlborough District Council on Wednesday afternoon.
Civil Defence Controller Mark Wheeler, told Morning Report it was done to enable police to force unwilling residents to leave their homes.
Some 35 people in Picton were evacuated on Wednesday night from a camping ground and from houses near a flooded creek.
They spent the night in the auditorium of Queen Charlotte College. Red Cross volunteer Sam Morrison told Morning Report their morale is good.
Checks will be made at first light for flooding and fallen trees in the town.
