Idaho local data guide

Boise, Idaho Climate and Year-Round Weather

Boise, Idaho, features a semi-arid climate characterized by four distinct seasons. The region experiences hot, dry summers and moderately cold winters with relatively low annual precipitation, typically averaging around 12 inches based on 1991–2020 climate normals.

Updated with grounded research as of 2026-07-21.

The short answer

Boise’s climate is defined by significant seasonal temperature variations and a semi-arid classification. Located in the Treasure Valley, the city typically sees hot, sunny summers and winters that are cold enough for snow, yet generally manageable compared to high-altitude mountain regions. The area is marked by a high frequency of sunshine, with over 200 sunny days annually, and precipitation that is most prevalent during the winter and spring months.

Key facts

Climate Classification
Semi-arid
Average Annual Precipitation (1991-2020)
Approximately 12.06 inches
Average Annual Snowfall (1991-2020)
17.6 inches

Seasonal Temperature Trends

Boise experiences distinct seasonal shifts. Summers (roughly mid-June to mid-September) are characterized by hot, dry days, frequently reaching 90°F or higher. Winters, by contrast, bring colder temperatures, typically ranging from highs in the upper 30s to lows in the mid-20s (°F). Transitions in spring and fall provide milder, temperate conditions often favored for outdoor activity.

Precipitation and Snowfall

As a semi-arid region, Boise’s annual precipitation is relatively light. While light rain occurs throughout the year, the wettest periods typically align with winter and spring. Snowfall is common but generally not excessive in the valley floor, with an average annual accumulation of 17.6 inches (1991-2020). Snow often melts relatively quickly in the valley due to urban heat retention and periodic sunshine, though icy conditions can occur overnight.

Geographic and Local Factors

Boise's climate is heavily influenced by its location in the Treasure Valley and the rain-shadow effect of surrounding mountain ranges. Cold air can become trapped in the valley during temperature inversions, which may lead to stagnant winter weather or persistent fog. Conversely, nearby foothills and mountain ranges, such as the Owyhees and the Boise Mountains, often receive significantly higher snowfall and lower temperatures than the city center.

Common questions

What is the average annual snowfall in Boise?

According to 1991–2020 climate normals from the National Weather Service, the average annual snowfall in Boise is 17.6 inches. While yearly totals can vary, snow in the valley rarely accumulates for long periods.

When is the best time to visit Boise?

For those seeking warm-weather outdoor activities, late June through early September is widely considered the best time to visit. Spring and fall are also popular for their mild, comfortable temperatures.

Does Boise experience extreme weather events?

Boise generally avoids extreme weather such as hurricanes or tornadoes. The most significant weather impacts are typically associated with winter inversions, which can trap cold air and moisture, or occasional heatwaves during the peak of summer.

Related Idaho questions

  • What are typical winter driving conditions in the Treasure Valley?
  • How do Boise's temperature extremes affect home utility planning?
  • What is the difference between valley weather and nearby mountain climate?

Sources and verification