How do you calculate degree days for a day?

• A. Average daily temp minus base temperature equals degree day accumulation for that day.
• B. Highest temp minus lowest temp equals degree day.
• C. Total rainfall multiplied by humidity equals degree day.
• D. Number of hours of sunshine equals degree day.

Answer: (A)

Degree days quantify how much heat is available relative to a base temperature, which is the threshold for development. For a given day, you take the day's average temperature and subtract the base temperature. That difference is the degree-day accumulation for that day. The base temperature is chosen for the organism or process; larger averages yield more degree days, and if the average is below the base, you would typically count zero for heating degree days or track cooling separately depending on the method. The other options don’t reflect heat accumulation: the temperature range, rainfall/humidity, or sunshine do not measure how much heat above a threshold the day provided.