If “normal” temperatures are calculated as a 30-year average, how is it possible to have jumps between daily normals?
In Canada, we calculate the daily normal high using the recorded daily high for the past 30 years. The high of the day before or the day after is not considered in the calculation. Through this averaging, extreme values will be included in the data set. Therefore, a day to day variation in the “normal” temperatures will occur. In the United States, the climatic normals are calculated differently. The high temperatures for each month are run through a statistical algorithm and the extremes are removed. After the variations are removed, the 30-year normal values are calculated. Thus, the result is a gradual change in normal values with no significant jumps.
