The effectiveness of a frost cover for plants lies in its ability to retain radiant heat from the ground. During the day, soil absorbs warmth from sunlight, and at night, this heat slowly rises. A properly installed cover traps that warmth around the plant, preventing cold air from settling directly on leaves and stems. This creates a buffer zone where temperatures remain several degrees higher than the surrounding air. Even a small temperature difference can be enough to protect plants from frost injury during short cold spells.