Hot-electron temperature (T-e) in InAlN/GaN high-electron-mobility transistors (HEMTs) was determined using electroluminescence spectroscopy as a function of gate voltage and correlated with the Te distribution determined by hydrodynamic simulations. Good agreement between measurement and simulations suggests that hot electrons can locally reach temperatures of up to 30 000 K at V-ds = 30 V, i.e., two to three times higher than that typically obtained for similar AlGaN/GaN HEMTs. The consequence of such high Te in InAlN/GaN HEMTs is illustrated by electrical stressing in OFF and semi-ON state at V-gd = 100 V. Prominent channel degradation was observed for devices stressed in semi-ON state, suggesting hot-electron driven degradation. Threshold voltage and drain current transient analyses indicate that hot electrons increase the density of traps in the GaN channel underneath the gate as well as surface/interface traps located in the gate-to-drain access region.