Boise, Idaho – Idaho residents are waking up to the coolest stretch of summer so far, with unseasonably low temperatures gripping much of the state through Friday. Morning lows and afternoon highs will run 10 to 15 degrees below average, especially across Baker City, Brundage Mountain, and Stanley, where Wednesday and Thursday mornings could see lows dipping into the upper 30s. According to the National Weather Service in Boise, isolated showers and thunderstorms are possible Thursday over Baker County and the West Central Mountains, but most communities will stay dry.
Major cities including Boise, Meridian, and Twin Falls can expect highs in the low to mid-80s through Friday, while Nampa and Caldwell will barely break 90, making it the coolest run since late spring. Roads should remain clear, but drivers in the high country—particularly near Mores Creek Summit and Sun Valley—should watch for changing weather if thunderstorms develop Thursday afternoon. Outdoor plans will feel more like early fall than August, so layering up in the mornings is smart, especially for early commuters and hikers.
The cooling trend flips sharply by Saturday, when hot air surges back and highs climb toward the 90s across the valleys. By Sunday and into early next week, monsoonal moisture could trigger more thunderstorms, especially in the mountains, so stay alert for updated advisories.
Idaho’s coolest summer stretch ends Friday, with temperatures and storm chances ramping up by the weekend.
Five Day Forecast for Boise, Idaho:
- Wednesday: Sunny, 59/89°F
- Thursday: Mostly sunny, 60/91°F, isolated mountain showers
- Friday: Clear and cool, 57/85°F
- Saturday: Hotter, 62/91°F
- Sunday: Hot, 67/94°F, increasing storm risk
