From AMS Glossary
- The condition that exists when the temperature of the earth's surface and earthbound objects fall below freezing.
Depending upon the actual values of ambient-air temperature, dewpoint, and the temperature attained by surface objects, frost may occur in a variety of forms. These include a general freeze, hoarfrost (or white frost), and dry freeze (or black frost). If a frost period is sufficiently severe to end the growing season (or delay its beginning), it is commonly referred to as a killing frost.
See frost day, ground frost.
See frozen ground.