If you live north of San Diego, you have to manipulate light and temperature indoors to get Christmas cactus to bloom on Christmas. Temperature An outdoor temperature of 70 to 80 degrees Fahrenheit during the spring and summer growing season is best, although the Christmas cactus can tolerate temperatures from 90 to 100 F. It will prosper with an indoor temperature of 65 to 70 F. Buds typically form by late October or early November.