Neither coleus nor impatiens will tolerate freezing. If it doesn't freeze too much they may just be damaged (look mushy) and then recover. If you don't get much cold I'm not sure about begonias, and it would also depend on the type of begonia and how cold it gets for how often. They'll likely go mushy somewhat too, even if not killed. Do you know what kind of begonias they are, or can you post a picture?
