A pleasant Friday evening in the 60s and 70s will slide into a pleasant night with mostly clear skies and lows dropping to the mid 40s by morning. Most of Saturday will be calm with clear to partly cloudy skies. Highs will be quite a bit warmer, reaching the upper 70s to mid 80s.
Thunderstorms will develop in Idaho during the late afternoon and evening. A few will cross the state line into Montana anywhere from the Bitterroot Valley to Bull Lake near the Sanders County/Lincoln County line during the evening. Most of these storms should be mild, but a stronger storm or two is possible in Mineral County. Saturday night will be mild with lows in the low 50s.
Conditions will be ripe for some strong thunderstorms Sunday afternoon and evening from the Idaho state line to as far east as I-15. High winds, large amounts of hail, and heavy rain are all possible with these stronger cells. Prolonged storm activity in one area on Sunday could lead to flooding of small streams since water levels across the area are pretty high. This will be a day to keep one eye on the sky if you're outdoors in the afternoon. The Bozeman area may see a storm or two but they will not be as strong. Temperatures will remain warm in the low 80s.
Rain and a few thundershowers is expected on Monday with highs only reaching the upper 60s and low to mid 70s. We dry out and warm up again in the middle of next week.