The eruption of Semeru Volcano on January 16, 2021, in East Java, Indonesia, posed a complex natural disaster. The response required adapting evacuation sites, routes, and emergency protocols while adhering to health guidelines. Most disaster preparedness studies use technical approaches under normal conditions, often neglecting health protocols. Our research focused on the Pronojiwo Sub-District in Lumajang, East Java, the area closest to Semeru Volcano and most at risk. We employed shelter plan analysis, spatial analysis, and numerical simulation. The study aimed to assess the affected area following Semeru’s eruption, considering critical factors like the impacted region, shelter availability, and evacuation routes. Numerical simulations revealed lava flows at 20 m/s with heights up to 3m. Notably, lava distribution exceeded predefined disaster-prone zones due to interaction with rainwater, extending beyond established boundaries. Shelter plan analysis indicated some shelters were unsuitable for temporary accommodation due to their location in areas affected by cold lava flows. Spatial analysis findings showed that shelter coverage areas remained insufficient to serve the residential zones around Mount Semeru impacted by the eruption’s material flow. This research will serve as a valuable reference for government authorities, helping them determine effective evacuation routes and suitable shelters for refugees during future Mount Semeru eruptions, ensuring the safety and well-being of affected communities.