Yearly and monthly probabilistic precipitations at 53 observatories in Japan are analized by cluster analysis. The yearly and monthly data analysed are of the stations which have data for more than 98 years. They are placed in ascending order and converted to probablistic precipitations by Weibll plotting position, i. e., the return period T is calculated by the formula ; T = i/(N + 1) (i : order number of the data arranged in ascending magnitude, N : number of data(years)). Firstly, six different clustering methodologies, namely, nearest neighbor method, furthest neighbor method, group average method, centroid method, median method and Ward method are applied to yearly probabilistic precipitation. Among these six methods, the nearest neighbor method gives a different dendrogram from others and among the rest, the furthest neighbor method seems to give a reasonable result from the point of view of ascending order magnitude of the clusters. By applying this method, it is found that the clustered districts do not coincide with such stereotyped geographical or meteorological districts as Hokkaido, Tohoku, Kanto, Hokuriku, Chubu, Tokai, Kinki, Chugoku, Shikoku, or Sanin, Setouchi, Nankai and Kyushu. Secondly, monthly probabilistic precipitations are analized by this method. The characteristics of precipitation, obtained from these cluster analyses, seem to provide useful information for rainfall utilization purposes.
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