Scattered thunderstorms with gusty outflow winds up to 55 mph will impact southern Idaho this evening before a brief warming trend pushes Treasure Valley temperatures back toward the upper 90s Tuesday and Wednesday. A gradual cooling trend will then develop through the end of the week, with a cold front potentially dropping temperatures below 80 degrees by Sunday.
Sizzling temps return ahead of weekend cool down in Scott Dorval's video forecast
Tonight: Thunderstorm Threat for Southern Idaho
Scattered showers and thunderstorms will develop over far southeast Oregon and southern Idaho this evening, generally from Burns, Oregon to the Owyhee Mountains to the Magic Valley. Strong gusty outflow winds up to 55 mph may accompany some storms. Storms will generally weaken into showers as they move northeast into the Snake River Basin, but gusty outflows and blowing dust will still be a threat for the Treasure Valley and surrounding areas. Showers will taper off overnight.
Outdoor plans for this evening should account for the possibility of sudden gusty winds and reduced visibility from blowing dust. Anyone attending outdoor events or activities in the Magic Valley or Treasure Valley should be prepared to seek shelter quickly if storms approach.
Tuesday and Wednesday: Heat Returns to the Treasure Valley
An upper-level ridge axis will remain just east of the area Tuesday and Wednesday, keeping southwest flow over the region and temperatures trending upward. The Treasure Valley will see highs near 96 degrees Tuesday and 97 degrees Wednesday. These temperatures are running about 5 to 8 degrees above the average high for late August in Boise, which typically sits around 89 degrees.
A weak wave will move over the region Wednesday, resulting in an uptick in winds mainly across southeast Oregon and a slight chance of thunderstorms across the central Idaho mountains and from the Magic Valley south to along the Nevada border. Outdoor and travel plans for the central Idaho mountains Wednesday afternoon should account for this storm threat.
Gradual Cooling Through the End of the Week
A welcome cooling trend will develop Thursday through the weekend. Temperatures will drop from 94 degrees Thursday to 89 degrees Friday and 86 degrees Saturday as a weak shortwave begins to break down the upper-level ridge. A slight chance of precipitation will develop Friday, mainly across the higher terrain of southwest and central Idaho.
Cold Front Brings Significant Cooldown Sunday
The most significant weather change of the extended period arrives Sunday as a low-pressure system drops down the British Columbia coast and sweeps past the area. This system and its associated cold front will bring a notable cooldown and increased precipitation chances, most pronounced in the central Idaho mountains. Temperatures on Sunday will likely swing below normal following the cold frontal passage, with the lower Snake River Plain having a 40 percent chance of the afternoon high falling below 80 degrees. This would be a dramatic change from the upper 90s earlier in the week.
For historical context, Boise's average high temperature for late August is around 89 degrees, and temperatures below 80 degrees in late August are relatively uncommon, occurring only about 20 percent of the time historically. Breezy conditions will persist throughout the extended period.
Tonight
Partly cloudy, with a low around 65. Light breezes becoming calm.
Tuesday
Increasing clouds and hotter, with a high near 96. Light wind.
Tuesday Night
Mostly cloudy, with a low around 67. Light wind.
Wednesday
Partly sunny and quite hot, with a high near 97. Breezy morning.
Wednesday Night
Partly cloudy, with a low around 66. Light wind.
Thursday
Mostly sunny and not as hot, with a high near 94. Breezy morning.
Thursday Night
Partly cloudy, with a low around 64.
Friday
Mostly sunny& cooler, with a high near 89.
Friday Night
Partly cloudy, with a low around 61.
Saturday
Sunny & pleasant, with a high near 86.
Saturday Night
Mostly clear, with a low around 55.
Sunday
Sunny & comfortably cooler with a light breeze, with a high near 82.
Sunday Night
Mostly clear, with a low around 55.
Monday
Sunny & warmer, with a high near 89.
