Widespread and persistent summer multi-day episodes of dense wildfire smoke affected western Canada in 2017 and 2018. These events often occurred under otherwise clear-sky, anticyclonic weather conditions and can have significant impacts on surface temperatures, air quality, and surface radiation and energy budgets. Based on upward-pointing lidar observations, vertical temperature soundings and numerical mesoscale modelling for a mountain in south-western British Columbia, Canada, we propose a previously undocumented stability-related impact of wildfire smoke layers on mountain meteorology. This positive feedback (that maintains layer structure and extends the lifetime of layers) appears to suppress mountain “handover processes”. Smoke days are characterized by more stable vertical temperature profiles when compared to clear-sky conditions, and are marked by a lack of diurnal variability in boundary-layer structure in lidar backscatter imagery. We expect the processes described to have general application and propose more detailed aerosol modelling to investigate the physical details of the process.