Abstract The initial interpretation of Galileo data from Jupiter's moon, Io, suggested eruption temperatures ⩾ 1600 ° C . Tidal heating models have difficulties explaining Io's prodigious heat flow if the mantle is > 1300 ° C , although we suggest that temperatures up to ∼ 1450 ° C may be possible. In general, Io eruption temperatures have been overestimated because the incorrect thermal model has been applied. Much of the thermal emission from high-temperature hot spots comes from lava fountains but lava flow models were utilized. We apply a new lava fountain model to the highest reported eruption temperature, the SSI observation of the 1997 eruption at Pillan. This resets the lower temperature limit for the eruption from ∼1600 to ∼ 1340 ° C . Additionally, viscous heating of the magma may have increased eruption temperature by ∼ 50 – 100 ° C as a result of the strong compressive stresses in the ionian lithosphere. While further work is needed, it appears that the discrepancy between observations and interior models is largely resolved.