If you spend enough time around veteran fly fishing guides in Montana, the weather, and its impact, are going to come up in conversation. From stories about bluebird days, twitching grasshopper patterns, to fishing through the rain on a great day of streamer fishing, the weather dictates fly fishing more than any other factor. With a variety of rivers and topography, going fly fishing in Montana during the angling calendar means you are going to experience nearly every type of seasonal weather. By early March, our guides are on the water more than they are not. And, by early November, most of our Montana fly fishing guides have wrapped up their seasons. Here is our guide to Montana's weather during the angling season.
During any month of the season, Montana fly fishing weather is highly variable with a wide range of temperatures and climatic conditions. Visions of casting dry flies under a clear blue sky may be what you want, but on any given day you may experience overcast and drizzle, a snow flurry, or that well-known big blue sky. In most years, March, April, and May, and again in October and November are the months with the greatest variance in daily conditions; and, June through September are the most consistent. In general the state has a drier climate and enjoys a lot of sunshine. Daily temperatures often fluctuate considerably and can change by 50 degrees from the morning to the late afternoon. Even in the peak of the summer, it is wise to bring rain gear, a fleece, and a winter hat just in case a summer thunderstorm hits.
March
Our local Montana fly fishing guides look forward to March every year. However, planning for going on a fly fishing trip in March is all about flexibility, including the possibility of not going fishing at all. Weather in March can range from daytime highs in the 20s to to 60s. Snow and freezing rain can occur regularly, so safety can always be an issue. Bottom line for fly fishing in Montana in March, hope for the best but plan, and expect, the worst and always have a Plan B.
April and May
We lump April and May together because of Montana's varied topography and mini-climates. April in the Gallatin Valley near Bozeman has different weather than April on the Upper Madison near Yellowstone National Park. Spring weather can be beautiful. The mountains are still covered in snow, and the valleys begin to turn green in May. On nice days, the sun shines,s and the sky is crystal blue with highs in the 50s to 70s. Spring can bring in Pacific storms that tend to produce unsettled weather for two or three days at a time. When these storms roll in, it often drizzles off and on during the day with temps in the high 40s or low 50s. Wet snows are possible even in the valleys in the spring. It is important to bring layers and rain gear (our guides have extras!) in case one of these storms arrives. Fishing can be outstanding in the spring when the skies turn grey!
June
June is a major transition month. Storms are still moving in and the beginning of June still has potential to have some sustained wet weather. Montana isn't nearly as wet as the east coast or northwest however. By mid June high pressure begins to set in and precipitation is limited to passing thunderstorms and the occasional front
July and August
July and August bring gorgeous summer weather. This is a dry time of the year and precipitation is generally limited to the occasional passing thunderstorm. Once in a blue moon a front moves in and brings sustained drizzles for a day or so but these are rare (but bring awesome fishing!). Average highs are in the 80s in the summer but we occasionally get heat waves. Temperatures in the 90s are considered hot and temperatures in the low 100s are very rare but possible.
September
September is a transition month. The month is dry and the daily temps are usually very pleasant with highs in the low 80s and 70s. Occasionally an early fall storm moves in to bring chilly weather. Valley snow is very rare in September.
October
October is another transition month. It is still very dry but as fronts move in a day of rain or snow is possible. Temperatures at the beginning of the month are usually very pleasant. On most years October produces great fall weather during the entire month but on some years early winter storms move in late in the month. Fishing is awesome in October but make sure to bring warm layers just in case. The weather never shuts down the fishing but it is important to be prepared so that you are still comfortable if cold weather arrives early.
