Abstract: Previous analyses have focused on the relationship between sea surface temperatures (SSTs) over tropical oceans and summer typhoons over the western North Pacific (WNPTYF); however, few studies have been conducted on other oceans. To determine the relationship between the WNPTYF and SSTs over the middle-high latitude Indian Ocean (MHIO), their independence, significance, and hysteretic characteristics are examined in this study. The results show that SSTs over MHIO can influence WNPTYF independently when the effect of El Ni?o-Southern Oscillation (ENSO) is not considered. The annual change in SST over MHIO can indicate WNPTYF’s yearly change, in addition to that over the tropical East Pacific, with greater accuracy. Synthesis of the SST anomalies over the two areas is useful when the WNPTYF forecast is abnormal. Results also show that SSTs over MHIO influence WNPTYF in hysteresis, with significant correlation in the previous stage, from January to April, and week correlation at the same time, from June to September. The lagged influence of SSTs over MHIO to WNPTYF indicates that the former affects the latter through continuity of the abnormal atmospheric action over the Southern Hemisphere rather than by SST steadiness. However, for better understanding of this mechanism, further research is required.