An examination of the frost data for Alberta has shown that the mean frost-free period for the years 1951–1964 differed from the mean for the years prior to 1951. The difference was greatest in the basin of the North Saskatchewan River from Edmonton eastward, where the period increased by three or four weeks. The increase was less in southern Alberta, and some stations here showed no significant change. In the northern half of the province, the length of the frost-free period increased on the average by nearly three weeks.