The Treasure Valley will enjoy two more beautiful days Friday and Saturday before a powerful cold front sweeps through Saturday evening, bringing gusty winds, showers, and a dramatic temperature drop that will make Sunday feel like a completely different season.
Gusty winds and cooler temps are on the weekend horizon, but which day?
Friday and Saturday: Enjoy the Warmth
Friday will bring sunny skies and a high near 81 degrees, still running well above the normal high of around 81 degrees for mid-September in Boise. Saturday will be even warmer, with highs near 87 degrees as strong southwest flow ahead of the approaching Pacific upper low keeps temperatures about 10 degrees above normal. Both days will offer excellent outdoor conditions with light winds and clear skies.
A dry cold front will sweep across the area this evening, bringing some elevated westerly winds through around sunset. Breezy conditions will return Friday afternoon but temperatures will remain warmer than normal.
Fire Weather Concerns Saturday
The strong southwesterly winds Saturday, with gusts up to 45 mph near the Idaho-Nevada border, combined with low relative humidity values, will bring heightened fire weather concerns for southern areas. Residents near the Nevada border should be aware of the elevated fire danger Saturday afternoon and avoid any activities that could spark a fire.
The Big Event: Powerful Cold Front Saturday Evening
The most significant weather event of the week arrives Saturday evening as a powerful cold front sweeps through the region. Wind gusts of 35 to 45 mph will impact southern areas, with widespread showers and scattered thunderstorms developing across the northern half of the region. The west-central Idaho and east-central Oregon mountains will see the highest chances of heavy rain and embedded thunderstorms.
For the Treasure Valley, total rainfall will be modest at around 0.01 to 0.05 inches, with a 10 to 15 percent chance of thunderstorms late Saturday through early Sunday. While the valley will largely escape the heaviest precipitation, the gusty winds will be the primary concern.
Sunday: Dramatically Cooler
Sunday will feel like a completely different season compared to Saturday's 87-degree warmth. Temperatures will drop to a high near 68 degrees, running about 14 degrees below Saturday's peak. Snow levels will drop to the 7,000 to 8,000-foot range through Sunday morning, favoring some light snowfall over the highest mountain peaks. By late Sunday, western zones will clear, and Sunday night will be cold and mostly clear area-wide with lows near 46 degrees in the Treasure Valley. Valley fog is possible early Monday morning.
Recreation Forecast: Treasure Valley and Central Idaho Mountains
Friday: An excellent outdoor day with sunny skies and a high near 81 degrees. Breezy conditions over high terrain areas in the afternoon, but otherwise ideal for hiking, cycling, and outdoor activities.
Saturday morning and early afternoon: The best outdoor day of the weekend with sunny skies and a high near 87 degrees. Plan to be off exposed ridges and mountain summits by early afternoon as conditions will deteriorate rapidly Saturday evening with gusty winds and showers.
Central Idaho Mountains this weekend: The mountains will see the most significant weather impacts this weekend. Showers and thunderstorms will develop Saturday evening, with the central mountains of western Idaho and eastern Oregon seeing the bulk of the precipitation. Snow levels dropping to 7,000 to 8,000 feet means the highest peaks could see light snow Saturday night into Sunday. Hikers and campers in the backcountry this weekend should be prepared for rapidly changing conditions and have rain and wind gear readily accessible.
Sunday: Cooler and breezy with a high near 68 degrees. Showers will continue in northern mountain areas through the morning before tapering off in the afternoon. A good day for lower elevation activities in the Treasure Valley once the morning showers clear.
Looking Ahead: Warming and Drying Next Week
Monday will bring sunny skies and a high near 68 degrees before a large ridge of high pressure rebuilds over the Northwest, bringing a warming and drying trend through the rest of the week. Temperatures will climb from 72 degrees Tuesday to 77 degrees Wednesday under sunny skies and dry conditions.
Tonight: Partly cloudy, with a low around 58. Breezy this evening.
Friday: Sunny, with a high near 81. Wind NW 5-15.
Friday Night: Mostly clear, with a low around 55. North wind around 5 mph becoming light and variable after midnight.
Saturday: Sunny, with a high near 87. Light wind then gusty wind in the evening with a cold front.
Saturday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 52. Southwest wind 7 to 15 mph becoming northwest in the evening. Winds could gust as high as 30 mph. Chance of precipitation is 50%.
Sunday: Mostly sunny & much cooler with a breeze, with a high near 68.
Sunday Night: Mostly clear, with a low around 46.
Monday: Sunny, with a high near 68.
Monday Night: Mostly clear, with a low around 46.
Tuesday: Sunny, with a high near 72.
Tuesday Night: Partly cloudy, with a low around 49.
Wednesday: Sunny, with a high near 77.
Wednesday Night: Mostly clear, with a low around 53.
Thursday: Sunny, with a high near 82.
