Montana is a huge state with many different environments. The majority of the trout fishing is done in the areas near the mountains. The NW corner of Montana does have some good fishing opportunities and I would do some google searches for both Tim Linehan and Dave Blackburn. They both provide guide service in that area and it would at least give you ideas of some of the fisheries, which you could then do more research on. I am not plugging their guide services but it will at least give you a place to start for searching out places you could fish on your own.
As far as the Northern portions of Montana you will find a few places but not a lot because it is the praire. We call it the high line in Montana and it is primarily dry land crop producing land with only a few rivers that flow through the area. The Missouri, Milk and Marias are the primary rivers in the northern part of the state and they all generally flow dirty and provide only a few limited options for trout or fly rod anglers. Catfish, walleye and sauger dominate the fisheries in the northern part of the state.
Good luck with your adventure and let me know if you have any other questions about Montana.
Get a hold of the book, Montana's Best Fishing Waters. It is a part of a series, they make them for many states. I bought it at Bass Pro Shops last year for around $30. It is dead on accurate. It shows public access points, parking, and includeds the GPS coordinates with them. The maps are also annotated to tell you what kind of fish are in which spots during which seasons. I went to Montana last summer for the 2nd time, but this time with the book. It was incredibly accurate and helpful. Because of that book, I fished rivers like the Ruby that I never would have tried and had great success. Can't recommend it enough (and I have nothing to do with the book, there is no money in it for me).
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Sorry about the two posts but I just saw your response to Larry about Colorado, which is where I live and fish. If you decide on Colorado, send me a private message on this forum. You can fish year round here with all the tailwaters we have. The only time that can be sketch is June because runoff is massive and there are only a few limited places that aren't affected.
I did not decide yet. But have been focusing my search in MT now... But I have become very curious about it... reading a lot about the west and southwest portion of MT but no report about the rest!
I´ll also search about CO, WY and ID. About Colorado, I have been reading just a few, but have the impression that trout fishing is done more at the W and NW area, isn´t it?
Well, despite MT being considered a "Meca" for all flyfishermen, I am not so confortable about being there by Jul/Aug... I´d ratter go somewhere else... and let MT for another trip in the near future.
Larry, could you tell me how is it in CO this period? What about WADE fishing there, BESIDES boat/rafting fishing? Of course, If I decide for Colorado, I´ll try to book some days with you!
Alex: One thing to consider in your trip planning is river access. MT and ID allow fisherman to fish on private property as long as they wade below the high water mark of the river. That means as you travel on any public road in MT and ID and where a bridge crosses a river you can get out and start wading the river. In CO, WY and UT the landowner owns the river bottom so you are restricted to fishing on public access right-of-ways or on national forrest land, so in planning on primarily wade fishing MT and ID have huge advantages over the other states. That is the primary reason I bought a drift boat, so that I could travel away from the WY public access points which tend to get crowded. There are just too many truely fantastic rivers to fish in the Rockies so that will mean you will need to narrow your search down. If I were planning on fishing MT I would draw a line from Missoula to Helena to Billings and concentrate on the rivers to the south of that line. As Biggie said there is really good fishing in other parts of the state but the majority of the great rivers are in the SW region.
CO is another state with some really great waters: the Arkansas, the Gunnison, the South Platte (CO's Dream Stream), the Frying Pan, the Roaring Fork, the Colorado are all truely great streams and each has fairly decent public access.
For questions on ID fishing, I would send a PM to kglissmeyer1 (Kelly) and to Sahsa, both live and fish in ID. For UT questions I would send a PM to Fysh and Joni, they will be able to answer specific questions.
This is a big expensive trip you and your friend are planning and you will have limited time to explore all the waters that are available, so plan carefully and enjoy your trip. Keep asking questions we will try to answer them the best we can.
I have heard a few rumors of another great hopper year coming up so if you come in July/August you will be in prime hopper fishing, so be prepared with lots of hopper patterns.
About Colorado: Just to add to Bret and Larry's posts, anything west of Denver has a wide variety of fly fishing opportunities. I would generally classify some of the more famous waters as "technical" in nature, especially compared to Montana rivers. Many fish more like spring creeks because of water clarity, relatively low flows, and high pressure. However, with a little effort ant local knowledge, you can find just about any type of fishing you are after. The Taylor river has some of the biggest fish I have ever seen, but they are also some of the most difficult fish to catch. The Frying Pan is slightly less technical but still holds big fish. The Roaring Fork, Colorado, and Eagle are all bigger, more western feeling rivers with plenty of fish per mile. The Arkansas is a gem with lots of wild browns (some bigger than advertised). The South Platte has big, smart fish and a variety of types of water. Then there is the Cache La Poudre, the Blue, the North Platte headwaters, the Yampa tailwater, and about a thousand small streams that all have fish.
But they are not well kept secrets and all are very accessible, so....
it is generally combat fishing during peak times and on weekends.
The nice thing is, you can stay in certain towns (Glenwood Springs, Silverthorne, Salida) and be within an hour of two or three of the major rivers.
Missoula,Mt is a nice small city and college town. There are a number of great trout fishing rivers close by including the Clark Fork, Bitterroot, Blackfoot, Rock Creek, and just over the pass into Idaho, the Lochsa, and upper Clearwater Rivers.
Also, the Kalispel and Columbia Falls area of Montana near Glacier Park have the North Fork, the Middle Fork and the South Fork of the Flathead River. It could take all summer to fish all three of those rivers and the scenery is spectacular.