<p>Aqueous zinc metal batteries often encounter uncontrollable failure or performance decay under thermal environments, primarily due to the severe side reactions caused by aqueous electrolytes. Here, an organic-inorganic-H₂O multiphase aqueous soggy sand electrolyte is reported to enhance high-temperature performance of aqueous zinc metal batteries. Soggy sand components form strong interactions between the heterogeneous phases, reconstructing hydrogen-bond networks and forming water-deficient solvation structures, which greatly limits water activity and improves thermal stability, eliminating parasitic reactions and inspiring a uniform Zn deposition at elevated temperatures. As a result, multiphase aqueous soggy sand electrolyte enables aqueous zinc metal batteries to achieve an operating temperature of 140 °C, a lifespan of 1700 cycles, and a current density of 8 A g⁻¹. More importantly, the application of this electrolyte allows the stable cycling of Zn metal pouch cells under continuous operation at elevated temperatures. This work paves the path towards electrolyte design that enables aqueous batteries to cycle stably under thermal environments.</p>