Permafrost degradation has become a critical indicator of environmental changes. Precise temperature profiling is essential for monitoring these subsurface trends and informing mitigation strategies. This study focuses on the Sommeiller Pass monitoring station which utilizes three vertical boreholes equipped with 36 thermistors. To distinguish genuine thermal evolution from potential sensor drift three on-site metrological calibration campaigns were conducted. This work contributes to the development of best practices for high-accuracy cryospheric monitoring and long-term data comparability.