About a dozen houses have severe flood damage in the township of Amberley in north Canterbury.
Residents of many other houses are moving their possessions to higher ground as the water threatens to creep in.
Rain continues to fall. Amberley is one of the worst affected places in north Canterbury.
The region is now cut off with State Highway One shut both south and north.
About half of the town's businesses are shut, as are schools and pre-schools.
Civil Defence will meet again at 1130am on Thursday to assess the situation.
At Sefton, 12 residents were evacuated to the local school hall earlier.
Doug Archbold, a retired Cheviot farmer who's taken weather readings in the area for more than 40 years, assess the storm as a 1:20 or 1:30 year event.
State Highway one is also closed South of Christchurch, from Rakaia to Ashburton.
The National Crisis Management Centre in Wellington is monitoring the storm.
MetService has now issued a heavy rainfall warning for eastern Otago until early Friday morning. The Otago Regional Council says rivers there could flood.
Road & rail closures
The storm is causing disruption to road and rail links in the upper South Island.
State Highway One is closed from Ward near Cape Campbell to Saltwater Creek near Sefton.
The line between Picton - Christchurch line is closed due to slips, flooding and debris.
However, Cook Strait ferries are still sailing.
South of Christchurch, SH1 is closed from Rakaia to Ashburton. Parts of the inland highway are also closed.