Long-term paleoclimate reconstructions of temperature provide context for the magnitude of recent anthropogenic warming, help quantify the climate response to radiative forcing, and better characterize the range of natural variability. In North America, temperature-sensitive tree-ring proxy data remain sparse, which limits the spatial and temporal extent of these reconstructions. Here we present an analysis of yellow-cedar (Callitropsis nootkatensis) growth in Washington State (USA) and its relationship to climate. Combining empirical statistical analysis with a process model of xylogenesis, we show that tree-ring chronologies from three high-elevation sites in the North Cascades are primarily controlled by temperature. We then use these chronologies to reconstruct summer temperatures over the period 1333 to 2015 CE, adding a new proxy to the North American network of temperature-sensitive trees. Comparison with an existing large-scale spatial gridded reconstruction suggests this species offers important local and regional information on past temperatures.