In Colorado winter fly fishing is just as common as ice fishing because the season never closes. With over 300 days of sun and the average temperature being some where in the 40's, fishing is not as bad as you think.
There are many rivers throughout the state that have open water year round because of being a tailwater. Tailwater refers to the water directly downstream from a hydraulic structure like a dam. When water is released from the bottom of a lake it is warmer than the river it is flowing into, which keeps several miles downstream from freezing over.
The Big Thompson River is a good example of a local tailwater. The picture below was taken several miles down stream of the dam at Lake Estes. You can see all the openings through the ice on the left.
Colorado Trout Hunters, a guide service out of Denver, has a great article on winter fly fishing , including great place to go. Now that you have some ideas on where to go, let's talk about the gear. Having the right equipment will make the difference in how enjoyable the day will be. If you have cold hands or feet it will be hard to stay even if the fish are biting. Here is some of the gear I have gathered over the years.
Simms Wading Sock, 85% Merino Wool, 14% Nylon, 1% Spandex. This sock has been very warm, I just wish it went a little higher up my calf.
Men's Capilene® 3 Midweight Bottoms and Top. I don't get as cold so I went with a mid weight layer. When picking your weight just remember you might be standing in the river, not moving much.
Wright McGill Men's Waders. I choose these waders because of the 5″ wide back support system and how easily they convert to waist waders. I am fine without Neoprene but if you get cold easily you might look into a pair for your winter fly fishing.
I use an old beat-up sweater that I don't mind if it get ruined. I bought a Patagonia Nano specifically for snowshoeing and fishing but if you wear it under the waders the slick material causes the wader straps to fall off the shoulders.
Wright McGill Big Horn Wading Jacket. This jacket has a lot of great winter features like, lined hand-warmer pockets, two big fly box pockets and over-sized zippers. It feels a little bulky but has kept me warm in many a snowstorm.
Generic Beanie. I have had the same hat, that my wife hates, for several years. Get something warm and that covers the ears. You can also try a ball cap with a beanie over it keep the sun out of your eyes.
Simms Windstopper Foldover Mitt. I bought mine several years ago
and I like the new model better. They got rid of the velcro that holds
the mitt back and replaced it with a strap. This is easier on the nose
while winter fly fishing. These gloves are warm but can't get wet and
flies get hooked in them a lot. I may buy a pair of neoprene that have
finger holes this year to see if I like them better.
Size:18 and 20
Size: 18 and 20 (red and black)
Size: 18 and 20
Blue Winged Olives
Size: 18 and 20