BOZEMAN — A smoky start to the week will give way to increasing monsoonal moisture and a growing threat of thunderstorms across Southwest Montana. The greatest concern arrives Wednesday, when slow-moving storms could produce heavy rainfall and localized flash flooding around Butte, Bozeman, and surrounding mountain valleys. After the midweek storm window, a significant warmup develops, with temperatures climbing well into the 90s this weekend and fire weather concerns increasing.
MONDAY NIGHT
Quiet weather continues across Southwest Montana this evening. Butte, Bozeman, Dillon, Ennis, Helena, and surrounding valleys will see partly cloudy skies with mild overnight temperatures mainly in the upper 50s to lower 60s. Wildfire smoke will remain present at times, producing hazy skies but generally only minor impacts. The atmosphere remains too dry for thunderstorm development tonight.
TUESDAY
Monsoonal moisture begins lifting north into the region, bringing more clouds and increasing humidity levels across Southwest Montana. Bozeman and Butte should reach the lower 80s during the afternoon, while lower-elevation valleys warm into the middle 80s. Isolated to scattered afternoon and evening thunderstorms may develop over the mountains and nearby foothills, though many valley locations remain dry. Temperatures continue running above seasonal averages, especially overnight.
WEDNESDAY
This appears to be the most active weather day of the week for Southwest Montana. A plume of deeper monsoonal moisture combines with weak steering winds, allowing thunderstorms to move slowly across the region. Butte, Bozeman, Dillon, Virginia City, West Yellowstone, and the surrounding mountain ranges all face an increased risk of locally heavy rainfall. Areas near burn scars, steep terrain, creeks, and urban drainage systems should closely monitor conditions, as excessive rainfall could lead to localized flash flooding. Thunderstorms will be capable of producing frequent lightning, brief gusty winds, and torrential downpours.
THURSDAY
Additional showers and thunderstorms remain likely across Southwest Montana, though storm motions should become somewhat faster than on Wednesday. Heavy rainfall remains possible in isolated locations, but confidence is highest that the greatest flooding threat occurs Wednesday. Temperatures remain seasonably warm with highs generally in the 80s. Storms continue to favor the mountains and adjacent valleys during the afternoon and evening.
FRIDAY
The weather pattern begins shifting toward a hotter and drier regime. While scattered afternoon thunderstorms remain possible, coverage should be noticeably lower than earlier in the week. Temperatures climb into the upper 80s and lower 90s across many valleys, including Bozeman and Butte. Increasing westerly winds and decreasing humidity will begin elevating fire weather concerns, especially where rainfall has been limited.
SATURDAY
Summer heat takes control across Southwest Montana. High temperatures surge into the lower to middle 90s in many valley communities, running roughly 8 to 10 degrees above normal for late July. Sunshine becomes more dominant, and thunderstorm chances drop considerably. Outdoor recreation conditions will be favorable during the morning, but afternoon heat will become a growing concern. Hydration, shade, and frequent breaks will be increasingly important.
SUNDAY
The hot, mostly dry pattern continues. Much of Southwest Montana remain locked into above-normal temperatures, with highs well into the 90s in the warmest valleys and overnight lows remaining unusually mild. Smoke may occasionally contribute to hazy skies. Any isolated thunderstorms that develop would be high-based and capable of producing gusty winds with little rainfall.
MONDAY
Early next week looks very similar, with persistent warmth, limited thunderstorm potential, and continued fire weather concerns. Areas that miss out on meaningful rainfall during the midweek storm period may see an increasing risk of rapidly drying fuels as temperatures remain well above normal and afternoon breezes redevelop.
