The Waimakariri district is reportedly being evacuated immediately with the assistance of emergency services.
The Civil Defence state of emergency continues for Ashburton and Timaru districts with concerns the Ashburton River may still breach its stopbanks if heavy rain continues.
700 people from about 305 properties were evacuated overnight, primarily in the Selwyn and Waimakariri districts overnight.
Civil Defence continues to warn residents to stay away from floodwater, avoid travel unless absolutely necessary, and check on neighbours if it is safe to do so.
The communities of Selwyn Huts and Winchester are also being evacuated, while in North Canterbury a driver was found in a serious condition after his car was swept down the Ashley River.
More than 1000 homes are reportedly without power in Christchurch.
Calls for safety
Ashburton District residents are urged to avoid coming into contact with floodwater, as the Ashburton wastewater pond treatment facility has flooded and the health risk to the public is high.
Meanwhile, monitoring teams are out checking river levels and stopbank conditions alongside Civil Defence.
There are extensive breakouts on the Ashburton River, particularly around the Greenstreet, Shearers Crossing and Thompsons Track areas, and other locations along the upper tributaries.
Breakouts have been anticipated on the Selwyn River throughout the night.
Ngai Tahu and government operation
Acting Emergency Management Minister Kris Fa'afoi was in Canterbury alongside Civil Defence teams and Ngāi Tahu based at the Regional Emergency Operation Centre in Christchurch.
Fa'afoi says the iwi are a key part of the response to help those hundreds affected.
"In and around Ashley, where we're more focussed in terms of our large scale evacuations, Ngāi Tahu have been pretty critical in making sure that we set up our welfare centres, like Hakatere Marae is available for those who may not have anywhere to go in that area around Ashburton," says Fa'afoi.
Heavy rain and snow
The main focus of heavy rain will be north of the Rakaia River to the inland hills and ranges, with 50mm to 90mm of rain expected untill 7pm this evening.
Heavy rain is expected to cause dangerous river conditions and significant flooding.
Slips and floodwaters are likely to disrupt travel, making some roads may be cut off - possibly isolating communities.
Heavy snowfall is also expected in the area today.
For Civil Defence alerts and emergency contact information, go to the website here.