In early July 2018, western Japan experienced a catastrophic flood, and it was followed by a record-breaking heatwave. The casualties by each disaster exceeded 200 and 1000, respectively, and the economic damage, approximately 10 billion USD, was greater than any previous flood disaster. According to a report by the Japan Meteorological Agency, synoptic conditions causing the heavy rainfall is attributable to 1) enhanced moisture convergence and 2) the stationary Baiu front, and the heatwave was primarily due to 1) collective impacts of expanded the Tibetan High and the North Pacific Subtropical High (NPSH) and 2) largely “meandering” subtropical jet. In this study, we examine the extent to which these back-to-back extreme events are linked to intensification of event-to-event variability under global warming and whether they will change under stabilized warming conditions of +1.5 and +2.0 degree above preindustrial period.