What Is a Frost Date? “A frost date is the average date of the last light freeze in spring or the first light freeze in fall. “The classification of freeze temperatures is based on their effect on plants: Light freeze: 29° to 32°F (-1.7° to 0°C)—tender plants are killed. Moderate freeze: 25° to 28°F (-3.9° to -2.2°C)—widely destructive to most vegetation. Severe freeze: 24°F (-4.4°C)…