Fishing season on the upper Colorado River usually starts in late May and early June when the first salmonflies begin to flutter. River flows can be very high this time of year and the water can be very muddy, so it is sometimes better to fish this hatch on foot. While float fishing is possible at any level, it really turns on once the river drops below 2500 CFS in Kremmling. This usually happens sometime in late June or early July, just in time for the summer hatches of caddis and mayflies.
The summer float season on the upper Colorado River offers some of the most consistent fishing of the year. With grasshoppers, caddis, sculpins, and a variety of mayflies in the water on any given day, hungry, surface-feeding trout are usually easy to find. The hopper-dropper is the rig of choice for most guides on the Colorado River through the summer and early fall, with fish eating above and below the surface all day long. During the middle of the summer, many parts of Colorado experience a monsoon season that brings regular afternoon thundershowers. These daily storms deliver much needed cold water to the Colorado, but they also deposit large amounts of sediment into the river. Clear water on the middle and lower sections of river can be scarce during the monsoon season, so many fishermen spend their days on the upper portions of the river to avoid the mud.
As the summer turns to fall, the weather usually stabilizes a bit and the water clears up throughout the whole river. This can be a challenging time of year to fish because of the brown trout spawning season, but with a little patience and the right combination of bugs, big fish can still be caught during the fall fishing season. This is also the time of year that the lower river’s temperature falls back into an acceptable fishing range.
Throughout the coldest parts of the winter, much of the upper Colorado river freezes solid. Open water on public property can be difficult to find, and hungry fish can be rare. Most Colorado River winter fishing trips take place on the lower river below the confluence with the Roaring Fork at Glenwood Springs. Here, midges flutter and dance along the water’s surface almost every day, and eager trout often rise to the surface to sip them down. Most anglers prefer to fish the lower Colorado from a boat, meaning that there is not very much competition for wade fishing spots. Wade fishing on the lower Colorado can be very productive during the low flows of winter and early spring. Subsurface rigs work best, but the patient angler can, with a little luck and the right weather, catch fish on dry flies here and there through much of the winter season