FROST

When the moisture in the air that is in contact with the earth is

condensed above the freezing point, dew is formed. When below the

freezing point, frost is formed or deposited on the earth. It is readily

understood from this that the surface on which the frost is deposited is

at a freezing temperature, while the air above it may not be freezing.

Naturally, you can expect frost when the temperature falls to a point 8°

or 10° above the freezing point. Clear, calm nights are favorable for

frost, because the absence of clouds helps radiation, that is, it draws

heat away from the earth. If there are clouds, it prevents this

radiation.