Cloudiness and wind speed as factors in a climatic anomaly

Since 1940, Calgary’s mean annual temperature has declined 0.3 °C from the mean value established during a warmer era, 1905–1940. However, the length of the frost-free period increased from an average of 109 days in the warmer period to 119 days in the cooler one. These changes are underscored by an advance of the probable date of the last spring frost, and a delay of the probable date of the first frost of autumn. Probabilities are computed for various critical frost dates. The belief is expressed that the discrepancy of a longer growing season in the face of declining growing season temperature is related to an observed increase in mean cloudiness during the growing season. It is also demonstrated that strong winds could have been a factor in promoting the anomaly.