Contained within the 4th Edition (1974) of the Atlas of Canada is a collection of five maps. Two maps show, for fertile regions, the average date of the last frost in spring and the average date of the first frost in autumn. The three remaining maps show the median depth of snow cover at a scale of 1:35 000 000 for all of Canada in inches for the dates September 30th, October 31st and November 30th.