While our normal date of first frost is around Thanksgiving, light frost was reported in outlying areas this year on Nov. 13 and 14, and heavy frost on the 15.
Frosts occur on still, clear nights.
Heat from the ground radiates to the sky, and the surface becomes colder and colder. When the surface reaches the freezing point, the layer of water vapor just in contact with the surface freezes into ice, and then the next layer above that, and so on. Frost develops earlier in the evening on your car, because metal and glass lose heat more rapidly than soil. Fog or cloud cover usually will prevent a frost by trapping the heat that otherwise would radiate out to the open sky. With less water vapor, the temperature continues to drop to levels that can damage many plants.