Although we are quite a ways south of the Duncans (almost in another country!), freezing isn’t rare around here. We are farther from the sea, so we get more cold and more heat, although less of either than most parts of the US. I knew a guy in my neighborhood who grew kumquats in a large container, and he only needed to wheel the container into a garage for about one week per year. We usually get down to 15-20 degrees Fahrenheit, and many, many days down to 25-30 or so. We can also grow limes, lemons, etc. that way.
John S
PDX OR