The Upper Boxelder Canyon river run in Wyoming is a challenging Class IV+ section of water that should only be attempted by experienced kayakers and rafters. The run features technical rapids, tight channels, and numerous obstacles such as boulders, fallen trees, and steep drops. The best time to float this section of water is in the late spring or early summer when water levels are high and range from 500-1500 CFS. However, due to the challenging nature of the run, it is recommended to go with a guide or experienced group.