Earthen sites of substantial significance have experienced considerable degradation. Chemical stabilization is a commonly used restoration technique, and temperature effects are a critical factor for this degradation, particularly for outdoor sites. However, significant gaps exist in research on the threats posed to stabilization materials by elevated temperatures. Therefore, this study investigates polyvinyl alcohol (PVA) as a representative organic stabilizer to examine the effects of temperature variations from 20 degrees C to 400 degrees C on mechanical properties and microstructure of PVA-stabilized soil. A combination of macro- and micro-scale characterization techniques, alongside theoretical modelling, is employed. The results show that constitutive models inspired by concrete effectively characterize the stress-strain behavior of PVA-stabilized soil under high-temperature conditions. Unconfined compressive strength of PVA-stabilized soil significantly decreases from 0.90-2.25 to 0.17-0.40 MPa as the temperature increases from 200 degrees C to 300 degrees C, which is attributed to structural changes of soil induced by thermal decomposition of PVA. The thermal degradation of PVA can generate harmful gases and cause a significant colour change. Therefore, organic materials like PVA are suitable for the restoration of earthen sites in non-fire-risk areas. However, caution is necessary when applying these materials in earthen sites at risk of fire hazards, especially those with vegetation cover.