This project characterized stream temperature regimes in the Cook Inlet, Copper River, and Prince William Sound regions. We aggregated 1,548 summertime stream temperature time series from 355 monitoring locations across southwestern and southcentral Alaska and calculated a suite of metrics related to the magnitude, frequency, duration, timing, and variability of stream temperatures. We categorized streams into one of six different thermal regimes. A comparison of stream thermal regimes among regions showed that cold habitats with later timing of maximum temperatures were most common in all regions, cold stable habitats were more common in the Copper River and Prince William Sound regions, and all regions included all six thermal regimes described in our classification.