It has been indicated that the occurrence of cold of hot summer over the nothern Japan is closely connected with prosperity and decline of the oceanic circulations in Tohoku sea region (Oyashio). On the other hand, it is also a well-known fact that the intensity of Oyashio is reenf orced by sea-ice on Okhotsk Sea. The author adopted the drift-ice periods at Abashiri and Shana by using a index on the Sea-ice intensity in Okhotsk Sea, and the annual deviations in drift-ice periods on both places are divided into five types for the sake of convenience.
From the significance test of differences between sample and population probability on each types, it became clear that cold-summer comparatively easy to occurs after SO-type (see Table 1) or L₂-types in its year (level of significance 25%), and hot-summer hard to occur after SO type by experience, etc. The detail of the methods of concrete statistical forecast on Sea-ice will be given in the next report.