A significant pattern change will bring cooler temperatures, periods of rain, and welcome moisture to the Treasure Valley and central Idaho mountains Tuesday through the weekend. This system could not come at a better time for firefighters and fire managers across the West, as the region has been dealing with an active fire season following weeks of record heat and dry conditions.
Cooler wetter weather is good news for fires in Scott Dorval's video forecast
Tuesday: Warm with Isolated Storm Chances
Tuesday will be the last warm day of the stretch, with highs near 88 degrees in the Treasure Valley. A slight 20 percent chance of showers and thunderstorms will develop between 1 and 3 p.m. Tuesday, with any storms capable of brief heavy rainfall, small hail, and gusty winds up to 50 mph. Breezy conditions will develop Tuesday with gusts of 15 to 30 mph, which combined with low afternoon humidity will produce elevated fire weather concerns across southern Idaho. Showers will increase overnight Tuesday into Wednesday as the pattern begins to shift.
Wednesday: Significant Cooldown Arrives
A shortwave trough will rotate across the area Wednesday, dropping temperatures about 10 degrees below normal to near 77 degrees in the Treasure Valley. Winds will remain elevated with gusts of 20 to 35 mph. Another shortwave trough will approach from the west Wednesday night, bringing another round of showers to west-central Idaho.
Thursday: Best Rain Chances for the Treasure Valley
Thursday will be the most significant precipitation day for the Treasure Valley, with a 50 percent chance of showers as an upper low spins over the Pacific Northwest. Temperatures will cool another few degrees to end up 10 to 15 degrees below normal, with highs near 73 degrees.
Estimated Rainfall Amounts:
| Location | Estimated Rainfall Wednesday Night Through Thursday |
|---|---|
| Treasure Valley (Boise area) | 0.05 to 0.25 inches |
| Central Idaho Mountains | 0.50 to 1.00 inches, locally higher |
| West-Central Idaho Mountains | 0.75 to 1.25 inches |
| Magic Valley | Minimal, less than 0.10 inches |
How This Rain Could Help the Fire Situation
This week's precipitation event could provide meaningful relief to an exhausted firefighting community across the West. The central Idaho mountains, which have seen some of the most active fire behavior this summer, stand to receive the most significant rainfall totals of 0.50 to over 1 inch. This level of precipitation can:
- Significantly reduce fire behavior and spread rates
- Lower fire danger ratings from critical to moderate levels
- Provide relief to firefighters who have been battling blazes in extreme heat
- Help improve air quality by washing smoke particles from the atmosphere
- Reduce the risk of new fire starts from lightning
The Treasure Valley will also see beneficial rainfall, though amounts will be more modest. Even a quarter inch of rain can help reduce fire danger in the surrounding foothills and improve air quality across the valley.
Weekend Outlook: Below-Normal Temperatures and Lingering Shower Chances
Additional impulses will rotate around the main upper low stalled across the Pacific Northwest through the weekend, bringing rounds of showers with thunderstorm potential each afternoon and evening. Temperatures are expected to remain below normal through the weekend, with highs in the mid to upper 70s Saturday and Sunday. A gradual warming trend is forecast by the weekend into early next week, with Labor Day highs near 80 degrees.
Forecast confidence late in the period is lower than normal due to potential interaction between tropical activity off the coast of Baja California and the upper low over the Pacific Northwest. There is potential for entrainment of tropical moisture under southerly flow aloft, which could enhance precipitation totals, but models vary considerably.
Tonight
Mostly clear, with a low around 62. Calm wind becoming east 5 to 8 mph after midnight.
Tuesday
A slight chance of showers and thunderstorms between 1pm and 3pm. Partly sunny, then gradually becoming sunny, with a high near 88. East southeast wind 6 to 10 mph becoming west northwest in the afternoon. Winds could gust as high as 21 mph. Chance of precipitation is 20%.
Tuesday Night
A 30 percent chance of showers after midnight. Increasing clouds, with a low around 58. North northwest wind around 6 mph becoming light and variable after midnight.
Wednesday
Cloudy, then gradually becoming mostly sunny, with a high near 77. Light and variable wind becoming southwest 5 to 7 mph in the morning.
Wednesday Night
A 30 percent chance of showers after midnight. Mostly cloudy, with a low around 56. Southwest wind 5 to 7 mph becoming light and variable.
Thursday
A 50 percent chance of showers. Mostly cloudy, with a high near 73.
Thursday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 51.
Friday
A 20 percent chance of showers. Partly sunny, with a high near 74.
Friday Night
A 20 percent chance of showers. Mostly cloudy, with a low around 52.
Saturday
Mostly sunny, with a high near 78.
Saturday Night
A 20 percent chance of showers. Partly cloudy, with a low around 53.
Sunday
A 20 percent chance of showers. Mostly sunny, with a high near 79.
Sunday Night
A 20 percent chance of showers. Partly cloudy, with a low around 54.
Labor Day
A 20 percent chance of showers. Mostly sunny, with a high near 80.
