This will depend on the weather forecast, but it is best to be prepared for anything. In general, think layers! What you will be wearing will depend on what section of river we are running, as there are very cold whitewater sections, as well as long scenic stretches. Light long underwear, quick dry shorts or pants, synthetic layers, quick dry sun shirts, and heavy duty rain gear should cover most of the weather patterns. In Alaska, rains can get heavy, so it is recommended to look into rubber, non-Gortex options to stay dry (which are often actually cheaper.) There are also extremely high UV indexes in Alaska this time of year, so brimmed hats and eye protection are also important. Quick-dry clothing, layers, rain gear, and sun protection are the most important things to keep in mind.