Enter the average daily temperature and the number of days into the calculator to determine the freezing degree days.

Freezing Degree Days Calculator

Enter any 2 values to calculate the missing variable (when uniquely determinable)

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Freezing Degree Days Formula

The following formula is used to calculate the freezing degree days for a given average daily temperature and number of days.

FDD = \max(0, 32 - T_{avg}) \times D

Variables:

  • FDD is the freezing degree days (°F·days)
  • Tavg is the average daily temperature in degrees Fahrenheit (°F)
  • D is the number of days

To calculate the freezing degree days, subtract the average daily temperature from 32°F (and use 0 if the result is negative), then multiply the result by the number of days.

What are Freezing Degree Days?

Freezing degree days (FDD) are a measure used in various fields such as agriculture, meteorology, and construction to quantify the severity of freezing conditions over a period of time. For each day, the daily freezing degree days are typically calculated as the number of degrees the average daily temperature is below the freezing point (32°F), with values above freezing counted as zero. Total FDD over a period is the sum of the daily values (and, if the temperature is assumed constant over the period, it can be approximated as FDD = max(0, 32 − Tavg) × D). This metric helps in understanding the cumulative effect of freezing temperatures on crops, infrastructure, and other systems sensitive to cold weather.

How to Calculate Freezing Degree Days?

The following steps outline how to calculate the Freezing Degree Days.

  1. First, determine the average daily temperature (Tavg).
  2. Next, determine the number of days (D).
  3. Next, calculate the freezing degree days using the formula FDD = max(0, 32 − Tavg) × D.
  4. Finally, calculate the Freezing Degree Days.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Average daily temperature (Tavg) = 25°F

Number of days (D) = 10