However, you could convey the concept of frost using a combination of signs:
* "Cold" sign: Make a "C" shape with your dominant hand and touch your chin.
* "Ice" sign: Make a fist with your dominant hand and tap your palm with your index finger.
* "On" sign: Make a flat hand with your dominant hand and tap it on your non-dominant hand.
You could combine these signs to say something like "cold on ground, ice" to indicate frost. You could also use a descriptive sign like "white, tiny, crystals on ground" to illustrate the appearance of frost.
Ultimately, the best way to sign "frost" will depend on the context and your individual signing style.