BOISE, Idaho – Halloween in the Treasure Valley has a long history of temperature twists — ranging from balmy afternoons to frosty trick-or-treat nights — showing just how unpredictable fall can be across southwest Idaho.
According to historical climate data compiled by the National Weather Service in Boise, Halloween highs have varied from a warm 74°F in 2012 to a frigid 13°F in 2002, marking the region’s coldest Oct. 31 on record. The typical daytime high lands near 56°F, with nighttime lows averaging around 36°F.
The city has also seen its share of wet and even snowy Halloweens. The wettest occurred in 1896 with over half an inch of rain, while 1971 brought the snowiest, when an inch fell on trick-or-treat night. Despite these extremes, about half of Boise’s Halloweens historically remain dry and crisp — perfect for costumes and outdoor festivities.
Forecasters note that fall in Boise often brings clear, cool evenings after sunny days, making for variable conditions between day and night. Long-range climate patterns suggest late October temperatures will continue trending near seasonal averages in the mid-50s through early November.
Residents heading out for Halloween should plan for layered costumes, as desert-like temperature swings can mean a 30-degree difference between afternoon highs and late-night chills.
