textproduct: Boise

UPDATE

Updated aviation discussion.

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 over the mountains of southwest Idaho early in the week.

SHORT TERM /Through Saturday Night/

Issued 358 AM MDT THU AUG 20 2026 The heat is on for the the next couple of days as an upper ridge intensifies over the area. Most lower elevation sites will see high temperatures top out between 96 and 104 today and Friday. A couple of caveats will be smoke and cloud cover, especially as we get into Friday. For now it doesn't look like smoke gets thick enough to impact temperatures (of course dependent on any new fire activity). High cloud cover later today and more so on Friday will likely take a couple of degrees off of heating potential which puts widespread 100-103 temperatures in the Treasure Valley. Elevated moisture on Friday will feed afternoon shower and thunderstorm development over higher terrain along the NV border which then propagates northward through the evening. A slight chance of thunderstorms is maintained across much of the area through Friday night due to the passage of a shortwave trough. A deeper low offshore lifts through the Pac NW on Saturday, cooling temperatures 5-10 degrees from Friday while keeping a chance of showers and thunderstorms in place for most sites. Gusty outflow winds are the dominate storm threat Friday and Saturday with greater moisture on Saturday increasing the heavy rain potential across SW Idaho. Winds will ramp up Saturday afternoon bringing 25-35 mph gusts to SE Oregon. A cold frontal passage Saturday night will shift winds to the northwest.

LONG TERM /Sunday through Thursday/

Issued 358 AM MDT THU AUG 20 2026 Dry air behind the front will limit shower and thunderstorm development to the ID/NV border area and eastern Boise Mtns on Sunday. Temperatures will run 4-8 degrees cooler than Saturday, placing lower elevations around 90 degrees, which is near normal heading into late August. For next week, we'll remain on the northwest fringe of a broad ridge centered over NM. Early in the week flow around the ridge will keep moisture over southern and eastern areas, supporting a 20-40% chance of showers and thunderstorms over higher terrain of southwest Idaho. By Wednesday drier air will cut off precipitation chances for most areas. Temperatures are back above normal next week.

AVIATION /12Z Thursday through Friday/

Issued 537 AM MDT THU AUG 20 2026 VFR with increasing high clouds in the afternoon. Some reduction in visibility due to wildfire smoke. Isolated high- based showers/storms along ID/NV border this afternoon. Surface winds: 10 kt or less, becoming SW-NW 5-15 kt after 18Z. Winds aloft at 10kft MSL: SW 10-25 kt.

KBOI...VFR with increasing high clouds in the afternoon. Hazy conditions due to wildfire smoke. Light surface winds through Friday.

Weekend Outlook...Scattered showers and thunderstorms late Friday through Saturday. Gusty outflow winds and locally heavy rain will accompany storms. Drier conditions Sunday. Local reductions in visibility due to wildfire smoke through the weekend. Gusty SW winds Saturday across SE Oregon, then breezy NW winds all areas on Sunday.

BOI WATCHES/WARNINGS/ADVISORIES

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