A degree day is an important weather phenomenon as it helps to calculate the degree of hotness or coldness. A degree day calculates the requirement of energy for heating of cooling buildings. It is a quantitative index which is calculated by observing temperature readings on a daily basis.

Importance of Degree Days:

A complete number of degree days beginning from a particular date are employed by agriculturists to decide the time of planting crops. It is also used to devise the appropriate way of managing pests. This can be explained by the fact that living organisms develop at a certain optimum temperature. Plants, insects and other pests need a requisite quantity of heat to move through the various stages of their life cycles. This is known as physiological time which is generally expressed in units of degree days. Organisms have upper and lower thresholds of development which are different for different species.

A degree day is sometimes called a heat unit and it is the collective product of temperature and time between thresholds required for development in a day. A degree day is 24 hours and it's temperature is one degree above that which is marked for the lower threshold of development.

Various Methods of Degree Day Calculation:

•  Triangle Method

•  Sine Method

•  Cutoff Method

•  Huber's Method

Each method differs in complexity and they change according to different climatic regions and seasons.

Functions of Degree Day:

•  It helps in agriculture and pest management

•  It is used to keep a check on the costs for heating or cooling a building that is controlled by climate.