Boise, ID – Summer heat is finally giving way to fall this week across southwest Idaho, with the National Weather Service (NWS) forecasting the last day of 80-degree highs on Monday. Starting Tuesday, residents across the Treasure Valley and nearby mountain towns can expect cooler afternoons and crisp mornings.
According to the NWS Boise office, Monday will be the final warm day for much of the region, with Boise forecast to reach 85°F and Nampa and Caldwell expected to climb into the low 80s. By Tuesday, highs across the area will fall into the 60s and 70s, marking a clear seasonal shift.
Morning lows will also dip noticeably, especially in higher elevations. Stanley, McCall, and Sun Valley are forecast to see temperatures in the 30s by midweek, while valley locations like Meridian, Caldwell, and Twin Falls will start mornings in the 40s.
The cooler trend continues through at least Saturday, with no locations in southwest Idaho expected to reach 80°F again. By Thursday and Friday, Boise is forecast to stay in the low to mid-70s, while mountain communities will see highs in the 50s.
For residents, the forecast means sweater weather, changing leaves, and a break from summer’s extended heat. Outdoor activities may feel brisker in the mornings, but afternoons should remain comfortable for early fall events.
