Extreme heat constrains global rice production. Polyploidy, a central driver of flowering plant evolution, is frequently associated with enhanced resilience to adverse environments. However, the epigenomic and transcriptomic programs that support heat tolerance in autotetraploid rice remain largely unexplored. In this study, we compared a diploid japonica rice line (GFD 2X) and its isogenic autotetraploid counterpart (GFD 4X) under short-term heat stress and subsequent recovery using physiologic