A degree is a measure of heating or cooling. Total degree days from an appropriate starting date are used to plan the planting of crops and management of pests and pest control timing. Weekly or monthly degree-day figures may also be used in an energy monitoring and targeting scheme to monitor the heating and cooling costs of climate controlled buildings, while annual figures may be used for estimating future costs. A degree day is computed as the integral of a function of time that varies with temperature. The function is truncated to upper and lower bounds, which are appropriate for climate control. The function can be estimated by one of the following methods, in each case by reference to a chosen base temperature: Heating degree days are typical indicators of household energy consumption for space heating. The air temperature in a building is on average higher than that of the outside air. A temperature of indoors corresponds to an outside temperature of about. If the air temperature is below 15.5 ° C, then heating is required to maintain a temperature of about 18 ° C. If the outside temperature is below the average temperature it is accounted as 1 degree-day. The sum of the degree days and the period of heating are used in calculating the amount of heating required for a building. Degree Days are also used to estimate air conditioning during the warm season. A temperature of indoors corresponds to an outside temperature of about. If the air temperature is below 15.5 ° C, then heating is required to maintain a temperature of about 18 ° C. If the outside temperature is below the average temperature it is accounted as 1 degree-day. The sum of the degree days and the period of heating are used in calculating the amount of heating required for a building. Degree Days are also used to estimate air conditioning during the warm season. A temperature of indoors corresponds to an outside temperature of about. If the air temperature is below 15.5 ° C, then heating is required to maintain a temperature of about 18 ° C. If the outside temperature is below the average temperature it is accounted as 1 degree-day. The sum of the degree days and the period of heating are used in calculating the amount of heating required for a building. Degree Days are also used to estimate air conditioning during the warm season. The sum of the degree days and the period of heating are used in calculating the amount of heating required for a building. Degree Days are also used to estimate air conditioning during the warm season. The sum of the degree days and the period of heating are used in calculating the amount of heating required for a building. Degree Days are also used to estimate air conditioning during the warm season.

Growing degree days are based on 5 ° C. Plants growth has been observed to date of growth. Many plants will be fruit after a certain number of degree days. Strawberries for instance. Other plants however, called deterministic, will be based on the day of sunlight in a day. Think of Easter golden lilies Christmas cactus. The paper referenced shows the complexity of plant growth and degree days.

Canadians use Growing Degree Days to predict when mosquitoes and black fly emerge and cease. For insecticidal growth, they are used. (0 ° C)

In the United States, a simplified method is used to calculate both heating and cooling. The mean (that is,) daily temperature in Fahrenheit and a nominal temperature of are used. If the mean daily temperature is 65 ° F, no degree days are counted. If the average daily temperature is below 65 ° F, the average degrees Fahrenheit below 65 ° F are counted as the heating degree day. If the average daily temperature is above 65 ° F, the average degrees Fahrenheit above 65 ° F are counted as the cooling degree day. The annual rate of heating and cooling is calculated as a percentage of total heating and cooling. Heating and cooling degree days closely correlated with heating and cooling demand.