Climate network reveals cross-seasonal teleconnections between heatwaves and cold waves.

Climate change is reshaping the global pattern of extremes, driving more frequent heatwaves, synchronous events, and compound hazards. This complexity renders the analysis and prediction of extreme events-such as heatwaves and cold waves-no longer confined to regional or weather-scale processes, as their interactions may trigger cascading and multiscale impacts. Using a complex network framework applied to global reanalysis data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (1981-2020), we identify robust cross-seasonal teleconnections linking boreal summer heatwaves with winter cold waves, despite their contrasting manifestations. These connections are modulated by large-scale climate modes such as El Niño-Southern Oscillation and the Arctic Oscillation, suggesting that the underlying dynamics transcend seasonal boundaries. This newly revealed relationship exposes previously unexplored correlations, enhances prospects for seasonal-to-interannual prediction of extremes, and underscores the pivotal role of large-scale climate modes in bridging summer and winter variability across hemispheres.