GeoOutageBench is a benchmark for assessing LLM-based geospatiotemporal KGQA for multimodal outage and resilience analysis. It considers a spatiotemporal KG that integrates visual, textual, and structured data from various sources. The benchmark provides a competency query taxonomy at different difficulty levels and evaluates three tasks: LLMs' understanding of ambiguous geospatiotemporal questions, ontology utility, and answer accuracy of multimodal KGQA retrieval.