A Heat Advisory remains in effect for the Treasure Valley as temperatures climb to dangerous levels Friday and Saturday, with Friday shaping up to be the hottest day of the stretch. Wildfire smoke will continue to blanket the region through at least Sunday, and a slight chance of thunderstorms will develop along the Idaho-Nevada border late Saturday.
Heat Advisory as triple-digit heat continues in Scott Dorval's video forecast
How Hot Will It Get? Comparing Forecast to Records
The forecast highs for Friday and Saturday are approaching historic territory for both Boise and Twin Falls. Here is how the forecast compares to all-time August records:
| Location | Record High (August) | Forecast Friday | Forecast Saturday |
|---|---|---|---|
| Boise | 111°F (Aug 10, 1898) | 103°F | 101°F |
| Twin Falls | 107°F (Aug 4, 1961) | ~103°F | ~101°F |
While the forecast highs will not challenge all-time records, they will be well above the average August high of around 96 degrees for Boise and 94 degrees for Twin Falls, running 5 to 10 degrees above normal.
Heat Advisory: Dangerous Conditions Friday and Saturday
The main upper-level ridge over the Great Basin will reach maximum intensity Friday, making it the hottest day of the stretch with highs near 103 degrees in the Treasure Valley. Saturday will remain dangerously hot near 101 degrees before a weak Pacific cold front begins to bring gradual cooling Saturday night. Overnight lows in the mid-60s will provide only limited relief, and areas with morning lows near 70 degrees will face Major Heat Risk.
Heat is the leading weather-related killer in the United States. Residents should:
- Stay hydrated by drinking water frequently, even if you don't feel thirsty
- Limit strenuous outdoor activities to the early morning hours
- Use air conditioning or visit a cooling center during the hottest parts of the day
- Never leave children, elderly individuals, or pets in parked vehicles
- Check on vulnerable neighbors, elderly family members, and those without air conditioning
Wildfire Smoke and Air Quality
Wildfire smoke will continue to impact the Treasure Valley and central Idaho mountains through at least Sunday. Smoke will be most concentrated during the overnight and early morning hours before afternoon mixing provides brief improvements. The Idaho Department of Environmental Quality and AirNow.gov provide real-time air quality information. Residents with respiratory conditions, the elderly, children, and others sensitive to smoke should limit outdoor activities and keep windows and doors closed.
Weekend Outdoor Recreation: Plan Carefully
For those planning outdoor activities this weekend, conditions will be extremely challenging. Afternoon wind gusts will be breezy Friday through Sunday, especially Saturday in southern zones as the cold front approaches. Combined with temperatures above 100 degrees, very low relative humidity, and wildfire smoke, these conditions will create elevated fire weather concerns.
If you must be outdoors this weekend, plan activities for the early morning hours before temperatures peak. Bring plenty of water, wear sun protection, and know the signs of heat exhaustion and heat stroke. Be aware of fire restrictions currently in place across the region. The Idaho Department of Lands and Bureau of Land Management have fire restrictions in effect for much of southwest Idaho.
A slight chance of high-based thunderstorms will develop along the Idaho-Nevada border late Saturday and Saturday night as high-level monsoon moisture advances northward. Any storms that develop could produce lightning on dry fuels and gusty outflow winds, creating additional fire weather concerns for Owyhee and Twin Falls counties.
Central Idaho Mountains
The central Idaho mountains will also experience dangerous heat Friday and Saturday, with temperatures running well above normal. Widespread smoke impacts will affect the mountains as well. Hikers and campers should be aware of fire restrictions and have an evacuation plan in case of new fire starts. The increased afternoon winds Friday through Sunday will create elevated fire weather conditions across the mountains.
A Bit of Relief Next Week
Gradual cooling will begin Saturday night as the weak Pacific cold front moves through. Temperatures will drop to near 98 degrees Sunday and continue moderating through the week, reaching the low 90s by Wednesday and upper 80s by Thursday. High temperatures should stay below 100 degrees through the extended period as the main upper-level ridge continues to slowly weaken and shift south.
Tonight
Areas of smoke. Mostly clear, with a low around 66. Light wind.
Friday
**Heat Advisory**. Sunny and very hot, with a high near 103. Light wind.
Friday Night
Areas of smoke. Mostly clear, with a low around 66. Light wind.
Saturday
Areas of smoke. **Heat Advisory** Sunny and hot, with a high near 101. Light wind.
Saturday Night
Areas of smoke before 5am. Mostly clear, with a low around 65.
Sunday
Sunny and hot, with a high near 98.
Sunday Night
Mostly clear, with a low around 64.
Monday
Sunny and not as hot, with a high near 96.
Monday Night
Mostly clear, with a low around 63.
Tuesday
Sunny and hot, with a high near 96.
Tuesday Night
Mostly clear, with a low around 64.
Wednesday
Sunny and hot, with a high near 93.
Wednesday Night
Mostly clear, with a low around 63.
Thursday
Sunny and very warm, with a high near 90.
