“Normals” is the term commonly used for values of climatic elements averaged over a fixed, standard period of years. The last standard international period set by the World Meteorological Organization (WMO) was 1961 to 1990. However the WMO recommends that countries should update their Normals every decade, using a 30-year period. In this vein, the Meteorological Service of Canada (MSC) prepared the Canadian Climate Normals for the period 1971 to 2000.

This paper describes the calculation methods used to develop the Normals. It includes a discussion of the MSC network and observational changes that occurred and the impacts on which stations and observational elements and summary information such as extremes were included. Normals were calculated for many locations for which complete data were not available for the 30-year period. A discussion is included on the impact on the use of fewer than 30-years to calculate averages to represent the Normals period. Finally, the publication of the Normals on the MSC web site is presented.