Abstract Permafrost extent (PE) and active layer thickness (ALT) are important for assessing high northern latitude (HNL) ecological and hydrological processes, and potential land–atmosphere carbon and climate feedbacks. We developed a new approach to infer PE from satellite microwave remote sensing of daily landscape freeze–thaw (FT) status. Our results document, for the first time, the use of satellite microwave FT observations for monitoring permafrost extent and condition. The FT observations define near-surface thermal status used to determine permafrost extent and stability over a 30-year (1980–2009) satellite record. The PE results showed similar performance against independent inventory and process model (CHANGE) estimates, but with larger differences over heterogeneous permafrost subzones. A consistent decline in the ensemble mean of permafrost areas (− 0.33 million km 2 decade − 1 ; p − 1 ; p 2 ) of permafrost areas are vulnerable to degradation based on the 30-year PE record. ALT estimates determined from satellite (MODIS) and ERA-Interim temperatures, and CHANGE simulations, compared favorably with independent field observations and indicate deepening ALT trends consistent with widespread permafrost degradation under recent climate change.