After a wet and cool week, the weather will deliver a stunning Saturday for the Spirit of Boise Balloon Classic before another round of showers and thunderstorms arrives Sunday night through Labor Day.
Unseasonably cool weather today will warm a bit for the weekend in Scott Dorval's video forecast
Tonight's Night Glow: Will It Happen?
The Spirit of Boise Balloon Classic Night Glow event is scheduled for this evening at sundown. The forecast shows scattered showers mainly between midnight and 5 a.m., meaning the evening hours around sundown should be mostly dry with a decreasing chance of precipitation. The 50 percent overnight precipitation chance is primarily focused after midnight, so the evening event window looks favorable for proceeding. Balloon Classic organizers should monitor conditions closely and check the latest forecast at weather.gov/boi.
Saturday: Best Day of the Weekend for the Balloon Classic
Saturday will be the highlight of the holiday weekend and the best day of the entire Balloon Classic. After areas of morning fog clear between 8 and 9 a.m., sunny skies will develop with a high near 75 degrees and calm winds. This is nearly ideal balloon flying weather, with light winds and clear skies expected through the afternoon. Balloon Classic attendees should plan to make the most of Saturday, as it will be the most favorable day of the event.
For context, Boise's average high for early September is around 84 degrees, so Saturday will still run about 9 degrees below normal, but the sunny skies and calm winds will make for a very comfortable and enjoyable day outdoors.
Sunday: Mostly Pleasant Before Storms Return
Sunday will bring partly sunny skies and a high near 77 degrees, with only a 20 percent chance of showers before noon. The morning and early afternoon will be suitable for outdoor activities and Balloon Classic events. However, conditions will deteriorate Sunday night as the upper trough begins to move inland, with an 80 percent chance of showers and thunderstorms developing Sunday night.
Labor Day: Wet and Cool
Labor Day will be a significant departure from the pleasant Saturday conditions. Showers are likely with a 60 percent chance of precipitation, and thunderstorms will be possible after noon. Temperatures will drop to near 68 degrees, running about 15 degrees below the seasonal average for Labor Day in Boise. Patchy morning fog is also possible. Keep outdoor plans flexible and have a backup plan for Labor Day activities.
Fire Season Relief: A Significant Week
This week's rainfall event has delivered the most significant moisture to the Treasure Valley and central Idaho since spring. The central Idaho mountains received 1 to 1.5 inches of rainfall, dramatically reducing fire behavior and spread rates across active fire complexes. Fuel moisture levels have increased substantially after weeks of critically dry conditions. Air quality across the Treasure Valley has improved noticeably as rain washed smoke particles from the atmosphere. The additional rainfall expected Sunday night through Labor Day will further enhance these fire suppression benefits.
Looking Ahead: Warming Trend Next Week
High pressure will build over the area Monday night as the upper low exits across Montana into southern Canada. Warmer air will return through the rest of the week, with temperatures approaching normal by Wednesday and beyond. Drier air will spread over the area Tuesday, but moisture will increase again later in the week as the next upper low approaches the Pacific Northwest coast while tapping into moisture from another westward-moving hurricane in the Pacific subtropics. A 20 to 40 percent chance of showers and thunderstorms is forecast Wednesday through Friday.
Tonight
Scattered showers, mainly between midnight and 5am. Mostly cloudy, with a low around 50. Light and variable wind. Chance of precipitation is 50%.
Saturday
Areas of morning fog. Otherwise, sunny, with a high near 75. Calm wind becoming west around 5 mph in the afternoon.
Saturday Night
Mostly cloudy, with a low around 52. Northwest wind around 6 mph becoming calm in the evening.
Sunday
A 20 percent chance of showers before noon. Partly sunny, with a high near 77. Calm wind becoming west northwest around 5 mph in the afternoon.
Sunday Night
A chance of showers and thunderstorms before midnight, then showers and possibly a thunderstorm between midnight and 3am, then showers after 3am. Low around 52. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Labor Day
Showers likely, with thunderstorms also possible after noon. Partly sunny, with a high near 68. Chance of precipitation is 60%.
Monday Night
Mostly clear, with a low around 47.
Tuesday
Sunny, with a high near 76.
Tuesday Night
Partly cloudy, with a low around 52.
Wednesday
Mostly sunny, with a high near 80.
Wednesday Night
Partly cloudy, with a low around 56.
Thursday
Partly sunny, with a high near 83.
Thursday Night
A 20 percent chance of showers. Partly cloudy, with a low around 58.
Friday
A chance of showers. Mostly sunny, with a high near 80.
