textproduct: Boise

KEY MESSAGES

- Heat Advisory Thursday afternoon through Friday in the Treasure Valley, western Magic Valley, and Upper Weiser River Valley.

- Increased chance of afternoon and evening showers and thunderstorms over higher terrain Friday through Sunday.

- Above normal temperatures next week with a chance of afternoon thunderstorms each day over the mountains of southwest Idaho.

SHORT TERM /Through Friday Night/

Heat Advisory continues in effect Thursday afternoon through Friday sunset as originally issued for the Snake Basin and Upper Weiser River Valley evening. However, high temps Friday have been adjusted down a couple degrees due to increasing clouds, especially on the Oregon side. Patchy smoke from wildfires will continue in eastern Oregon and northern mountains in Idaho with Friday morning the worst, although not nearly as smoky as 10 to 15 days ago. The first minor influx of monsoon moisture will bring isolated thunderstorms to northeast NV late today. Storms should stay south of ID but gusty outflow winds may reach southern Twin Falls County. A slightly stronger moisture surge will bring a 20% chance of showers and thunderstorms to Twin Falls County Thursday afternoon and evening. However, Friday is the day to watch as monsoon moisture increases further under stronger southwesterly flow aloft, due to a Pacific upper trough nearing the northwest coast. On that day after a very hot afternoon there will be a 20-30 percent chance of thunderstorms in eastern-most Idaho zones, and with lower atmospheric layers still dry these storms will again feature gusty winds and little rain.

LONG TERM /Saturday through Wednesday/

An upper trough moving across the PacNW on Saturday will bring a cold front and associated strong winds and increased thunderstorm chances. Wind gusts on Saturday increase to 20-35 mph across the area, highest in SE Oregon where minimum relative humidities around 10-20% will cause elevated fire weather conditions even though temperatures are cooler than Friday. Increased moisture ahead of the trough is amplified as it approaches, supporting a 20-50% chance of afternoon and evening thunderstorms across West Central and South Central Idaho, especially over the mountains. Storm chances stretch into the Blue Mtns of Eastern Oregon as well. Storms could produce lightning, strong gusty winds, and brief heavy rainfall.

The remainder of the extended period will be defined by the persistent Four Corners ridge which will place our region under southwest flow. Near normal temperatures Sunday, will be on the rise next week as the ridge rebounds. Latent monsoonal moisture circling the ridge maintains a 10-20% chance of storms and showers in South Central Idaho Sunday through Wednesday.

AVIATION /18Z Wednesday through Thursday/

Issued 1131 AM MDT WED AUG 19 2026 VFR under mostly clear skies. Areas of wildfire smoke across NE Oregon this afternoon. Surface winds: less than 10kt through tonight. Winds aloft at 10kft MSL: S 10-15 kt.

KBOI...VFR under mostly clear skies. Light surface winds through Wednesday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory from noon Thursday to 9 PM MDT Friday for IDZ012- 014-016-033. OR...Heat Advisory from noon MDT /11 AM PDT/ Thursday to 9 PM MDT /8 PM PDT/ Friday for ORZ064.