Sleeper Months in Big Sky Country

Sleeper Months in Big Sky Country

We thought about this post for a while and almost didnt write it.  The fact is, there are times of the year which have always been overlooked by visiting anglers, a not-so-well-kept secret by those who live and work in Montana (an ever increasing number), and we are hesitant to write about it. However, more and more people seem to inquire about fishing during the Sleeper Months”. So, we wanted to share some insights, and hopefully help people make informed decisions about planning their trip to Big Sky Country and get the most out of their time on the water.

The Early Season orPre-Runoff” period from Late-March through early-May is a dynamic transition from Winter to Spring in Big Sky Country, and most years it provides some terrific days on the water.  Daytime temps have begun to warm in earnest melting most, if not all, of the low-lying snow in our valley floors, but the bulk of winter snowpack remains locked up in the high country leaving rivers running low and clear. It is a time to be flexible, and prepared for any and all forms of weather from sun and 60 degrees to snowing sideways and temps in the teens.  Many days begin with plan A, and quickly devolve through plans C-D before culminating back in front of the wood stove and tying vise, or the local bar. When things do come together however, there is an opportunity for the fortunate few anglers (also an ever increasing number), who are in the right place at the right time with the right conditions, to experience some of the best fishing of the season.


The month of March is tricky.  Snow is still falling in the high country, hard at times, and the chances of super cold temps arriving is about as good as the Cubs not making it to the World Series.  March is usually warmer than Feb & Jan, and the fish are definitely waking up, especially in the lower elevation river valleys. This is a good month to ski a few laps in the am up at Big Sky, and hit the Gallatin or Madison Rivers in the afternoon if the daytime temps are in the high 30s or above. Or skip a couple of days on the slopes all together, and head up to float the Missouri.  March is midge month and they will rise if you search hard enough.  Trout also love to eat stoneflies, midge pupa, and worms this time of year. 


This is primetime in the Spring Pre-Runoff” period. Daytime temps are getting warmer and days are getting longer, but it can still be snowy in the high country.  Will the wind blow?  Of course, youre in Montana. Deal with it.  Cant cast in the wind?  Start practicing.  Your saltwater guide will thank you too.  Rivers across Big Sky Country are warming up and hatches of BWOs are consistent from the lower-Henrys Fork to the Madison, Gallatin, Yellowstone, and Missouri Rivers. Rainbows are still spawning, but on some lower elevation streams they are coming off their redds and beginning to hold in transitional Spring runs.  On the Madison around Ennis, and the Henrys Fork near Ashton, this is normally the month that the boat ramps are accessible, allowing float fishing to begin in our neighborhood.  Rubber legs, midges, or a dead drifted streamer will all produce sub-surface when the fish arent looking up for afternoon hatches of Baetis mayflies. 


May signals the beginning of the end of this short window as temps begin to warm in the high country, and the inevitable torrent of run-off begins. In some years this begins at the end of April. On others, we enjoy low clear water well into May. One thing is for certain though, Pre-Runoff” will transition into Mud Season” to some extent every May. Tailwater fisheries like the Henrys Fork and Missouri, where some of the dirtier effects of runoff can be avoided, become more important. The weather can still be un-predictable with ever increasing swings of the pendulum from warm Spring weather to cold Winter conditions. When clear water is present, hatches of Baetis mayflies and the infamous Mothers Day Caddis are not to be missed.

So, if you are among the ranks of those lucky soles who live within a drivable distance of our beloved Big Sky Country fisheries, or an intrepid angler from afar looking to experience the unpredictable beauty of springtime fishing in the Rockies, the Sleeper Months” of March, April, and May are well worth your attention. 

Another Sleeper Month” in Big Sky Country is the mid-summer month of August.


Yes, this is a sleeper month too…….many folks think that August is too warm and that the rivers are too low.  If the last two years have proven anything, its that August can be as wet as July.  There are several things about August that we love - spruce moths, ants, nocturnal stoneflies, and gulpers.  On the Madison, August is often less crowded and very fishy.  Spruce Moth activity begins at a gentlemanly hour around 9:30am. There are sections of the Madison where Spruce Moths are more consistent.  Remember, spruce moths are terrestrials, and where ever the river bottom meets pine forests, you will find them.  A size #12 Elk Hair Caddis works wonderfully during this hatch. Another interesting pattern to try is the size #12 Roger That from Category 3 Flies. We haven't seen epic numbers of Spruce Moths in recent years, but there were several days last summer that we were able to fish a moth imitation from ramp to ramp on the Madison.  For those early risers, getting up before the sun to fish a nocturnal stonefly close to the banks is good clean fun. Late in the afternoon we find it effective to fish a single dry fly on the Madison.  Either an ant or a hopper.  Since there are nocturnal stoneflies around, the hopper can cover both insects effectively. 

One of the highlights of our summer in Big Sky Country, Gulper season on Hebgen Lake is in full swing during the month of August. While the last two seasons have been slower than normal due to lots of wet days, and the corresponding lack of Callibaetis mayfly spinners, this is generally a wonderful place to spend a hot August morning before the afternoon winds pick up and send us in search of some terrestrial fishing. For anyone unfamiliar with Gulpers”, the term refers to large trout in Hebgen Lake (or any Stillwater for that matter) that rise to the surface to feed on freshly fallen Callibaetis mayfly spinners. Due to the size of the fishs mouth (these are large 16”+ trout), and the calm conditions, there is an audible Gulp” heard when the fish rise. When the fishing is good, trout will rise in rapid succession, allowing an angler to anticipate the next rise with a well-placed dry fly. This is not easy fishing as it requires a quick, accurate cast, not unlike saltwater fishing, but it is some of the most addictive and rewarding sight-fishing we have in Big Sky Country.

August is one of our favorite times to take a long walk and search for heads on the fabled Railroad Ranch section of the Henrys Fork. Crowds are at a minimum during August, and the resolute angler can almost always find a target or two with which to test their skills. Morning spinner falls, and ant flights are the highlights this time of year with hoppers providing some fun on windy afternoons. The pace is noticeably slower compared to the Hollywood Hatches of June, and there’s an intoxicatingly mellow rhythm throughout the fishery.

August is also prime time to explore the vast backcountry of Yellowstone National Park. When lower-elevation waters begin to warm and flows drop by mid-to-late-summer, high country fisheries in the Park are at their prime. This is the warmest, driest, least buggy time to be in the back country making it the perfect time to explore off the beaten path.

Honestly, Sleeper Months” are a thing of the past in Big Sky Country fishing. Weve seen a steady increase in angling pressure in recent years, and the fact that enough people are inquiring about fishing during the Sleeper Months” in and of itself would suggest that the proverbial Cat is out of the Bag. The truth is, March, April, May, and August are outside of the conventional “busy season” and well worth considering, but they are not the overlooked, under-explored months that one might think. Our hope is to help anglers get the most out of their experiences on the water, regardless of the season. So, if youre considering a trip in Big Sky Country during one of these months, or any other for that matter, give us a call in the shop, or drop us an email with any questions. We look forward to seeing you on your next trip!

- Joe Moore & Steve Hoovler, Big Sky Anglers

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