Montana weather can be highly variable with a wide range of temperatures and climatic conditions. 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 and a fleece and winter hat just in case a summer thundershower hits.
April and May
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 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 an 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 arrive. Fishing can be outstanding in the spring when the skies turn grey!
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 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 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.