The study documents the main controls of summer stream temperatures in a watershed identified as impaired due to high thermal loads. The most important controls examined are riparian vegetation height and canopy density, discharge, channel morphology, and surface inflows. The study uses data acquired from field measurements to evaluate stream temperature, channel morphology, and discharge, from LiDAR imaging data to describe riparian vegetation characteristics, and from a 10-m DEM to estimate surface inflows. These data are also inputs to Heat Source, a deterministic model that estimates changes in stream temperature for a segment of the stream by creating a thermal profile under existing conditions. The study uses a series of scenarios to assess the impact of the four identified factors and its implications for riparian restoration. The study results indicate that while riparian restoration is an important mechanism of lowering stream temperatures, it is insufficient to reach standards identified as conducive to viable salmon habitats. To attain this goal, the restoration of riparian vegetation must be paired with other approaches that lower the temperature of the incoming surface flows significantly.