Mountain breezes including katabatic and anabatic flows and temperature inversions are common features of forested mountain landscapes. However, the effects of mountain breezes on moisture transport in forests and implications for regional climate change are not well understood. A detailed instrumental study conducted from July to September 2012 in an even-aged conifer forest in the Oregon Cascade Range was investigated to determine how temperature profiles within the forest canopy influenced atmospheric surface layer processes that ventilate the forest. Within-canopy inversion strength has a bi-modal relationship to sub-canopy wind speed and resulting moisture flux from the forest. On days with relatively modest heating of the top of the canopy and weak within-canopy inversions, above canopy winds more efficiently mix subcanopy air, leading to greater than average vertical moisture flux and weaker than average along-slope, sub-canopy water vapor advection. On days with strong heating of the top of the canopy and a strong within-canopy inversion, vertical moisture flux is suppressed, and daytime downslope winds are stronger than average under the canopy. Increased downslope winds lead to increased downslope transport of water vapor, carbon dioxide and other scalars under the canopy. Increasing summer vapor pressure deficit in the Pacific Northwest will enhance both processes: vertical moisture transport by mountain breezes when within-canopy inversions are weak, and downslope water vapor transport when within-canopy inversions are strong. These mountain breeze dynamics have implications for climate refugia in forested mountains, forest plantations, and other forested regions with similar canopy structure and regional atmospheric forcings.