Abstract: In this paper the movement of the centers of deviations of the monthly mean pressure from the normal during the period of Jan. 1930-June 1939(total 114 months) are studied statistically. The centers of the deviations of the same month are found to concentrate at certain regions, such as south of Alaska, NE Atlantic ocean, Arctic coastal region of Eurasia, etc.(Fig. 1-4). These regions may thus be considered as key-areas for the occurrence of anomalous circulation over N hemisphere. The majority of these centers may be traced from month to month(Fig. 5-7). During the transitional seasons, most of the deviation centers are shifted from west to east. Some climatic peculiarities in certain regions of the northern hemisphere are discussed on the basis of the interaction of these monthly pressure deviation centers.