Rainfall-triggered collapses of hot lava domes are described relative to the fluid overpressurization that accompanies the infiltration of rainfall into the carapace. Similar rainfall-triggered modes of failure are apparent for both hemispherical (endogenous) and lobate (exogenous) domes. Failure modes for these disparate geometries are linked by the necessary incursion of rainfall into the hot dome and the resulting impeded drainage of interior gas pressures - either self-generated by the vaporizing infiltration front, or the impeded drainage of interior pressurized gases. Limit equilibrium models are developed to assess the stability of idealized hemispherical or lobate domes, with driving forces generated by interior gas overpressures. For endogenous domes, shallow failures may develop in the absence of gas pressurization from the core, but observed deep-seated failures require that the free escape of conduit gases be impeded. For exogenous domes, failure is driven to the base of the lobe by the desire to maximize overpressures.