Fire crews had to ferry more than 20 trapped people from a camping spot on the flooded Selwyn river, south of Christchurch late on Friday night. The operation took about two hours.
The Fire Service called just before 11pm to help a group of campers who were trapped by rising flood waters at Coes Ford, near Lake Ellesmere.
Police and fire crews spent two hours rescuing people on both riverbanks and towed a vehicle to safety.
Fire Service shift manager Rewai Grace said it appears the river levels rose sharply and took the campers by surprise.
Police say most of the campers then returned to Christchurch.
Earlier in South Canterbury, fire crews rescued a group of people who were trapped in their car in the swollen Kakanui River west of Oamaru, the scene of a dramatic rescue just hours earlier.
Five people were trapped in their car, near where a woman had to be rescued from the roof of her car by a farmer with a digger.
Three of the occupants were able to get out of the vehicle and swim to safety, but fire crews were needed to rescue the other two and towed the vehicle to safety at about 7.30pm.