Boise, Idaho – A sharp chill is sliding into southwest Idaho this morning, marking the Treasure Valley’s first real flirtation with freezing temperatures this fall. Clear skies and calm winds are setting the stage for a cold start Tuesday, when a Freeze Watch goes into effect for Boise, Caldwell, Nampa, and surrounding communities.
According to the National Weather Service in Boise, temperatures are expected to drop near or below freezing in outlying areas of the Snake River Valley between late Monday night and early Tuesday. Boise’s urban core may hold slightly warmer, around 35°F, but rural fields and foothill valleys will likely dip into the upper 20s. The agency warns that exposed crops, garden plants, and outdoor irrigation systems could be damaged if not protected.
Homeowners are urged to cover sensitive vegetation, bring potted plants indoors, and wrap or drain outdoor pipes. Those planning early commutes along I-84 or Highway 55 should watch for patchy frost on bridges and shaded roadways. For now, the chill will be brief — warmer, drier air returns midweek, bringing sunny afternoons and highs near the mid-60s through Thursday.
Looking ahead to the weekend, clouds begin to increase again as a Pacific system approaches. A few light showers could arrive by Friday night, signaling the next subtle turn toward early winter weather across southern Idaho. But before that, Tuesday morning’s first fall freeze will serve as a crisp reminder that autumn’s milder stretch is giving way — and the Treasure Valley’s growing season is officially on borrowed time.
Five-Day Forecast for Boise, ID:
Mon: 57/37 – Sunny and mild; light northwest wind.
Tue: 62/39 – Patchy frost early; sunny and calm.
Wed: 64/40 – Mostly sunny; seasonal warmth returns.
Thu: 66/46 – Partly cloudy; light south breeze.
Fri: 60/41 – Increasing clouds; late showers possible.
