Idaho local data guide

Hottest and Coldest Months in Boise, Idaho

Boise experiences a distinct seasonal climate, with July historically standing as the hottest month and January serving as the coldest based on long-term averages. Understanding these extremes is essential for planning seasonal home maintenance, energy usage, and relocation timing in the Treasure Valley.

Updated with grounded research as of 2026-09-08.

The short answer

Boise's climate is characterized by significant seasonal variance. On average, July is the hottest month, featuring average highs between 92°F and 93°F. Conversely, January is the coldest month, with average low temperatures typically ranging from 24°F to 25°F. While these represent typical yearly averages, Boise has experienced extreme temperature events, including an all-time record high of 111°F in 1960 and an all-time record low of -30°F in 1924.

Key facts

Hottest Month (Average)
July (Highs of 92°F–93°F)
Coldest Month (Average)
January (Lows of 24°F–25°F)
All-Time Record High
111°F (July 19, 1960)
All-Time Record Low
-30°F (December 25, 1924)

Understanding Boise's Seasonal Normals

When planning for relocation or evaluating a property's HVAC needs, it is important to distinguish between typical seasonal behavior and historical extremes. The data for these averages is based on the 1991–2020 climate normals. During a standard summer, residents can expect hot, dry conditions in July, while winter months—particularly January—bring the coldest air and the highest likelihood of freezing temperatures.

Extreme Weather Records

Boise's weather history includes notable deviations from typical averages. Historical observations taken since 1911 at the Boise Airport and surrounding stations have recorded significant temperature extremes that are important for local planning and infrastructure resilience.

  • The highest temperature ever documented in Boise reached 111°F on July 19, 1960.
  • The lowest temperature on record occurred on Christmas Day, December 25, 1924, dropping to -30°F.

Planning for Idaho's Climate

For homeowners and those moving to the area, the seasonal temperature range influences utility budgeting and home preparation. Winterization is generally prioritized in late autumn to prepare for January lows, while summer preparation focuses on cooling efficiency to manage the heat of July and August.

Common questions

Is January the only month with freezing temperatures in Boise?

While January is statistically the coldest month, freezing temperatures are common throughout the winter season in Boise, typically spanning from late autumn through early spring.

Do temperature records reflect current climate trends?

Current climate normals are calculated using the 1991–2020 period. While these provide the most reliable baseline for 'typical' weather, local climate patterns can shift, and these records are based on historical data collected at the Boise Airport since 1911.

Related Idaho questions

  • What is the average annual snowfall in Boise?
  • How many days of sunshine does Boise get per year?
  • What are the typical summer temperature ranges in Boise?

Sources and verification