The formula to calculate the Freezing Degree Days (FDD) is:
\[ \text{FDD} = (T_{\text{avg}} - 32) \times D \]
Where:
Let's say the average daily temperature (Tavg) is 20°F and the number of days (D) is 10. Using the formula:
\[ \text{FDD} = (20 - 32) \times 10 = -120 \]
So, the freezing degree days (FDD) is -120.