My cold frame temperature is getting up to 27*F (-3*C) or so with the midday sun on it, but it goes back down to bitter cold at night. It hasn’t gotten above freezing in several days now. The greens are wilted. I have broccoli, escarole, bok choi spinach, lettuce, parsley and rosemary growing inside it. I don’t know if anything will survive. It hasn’t gotten this cold since we built the cold frame.