Idaho local data guide

Average Climate for Boise, Idaho in August

Boise, Idaho, experiences a cold semi-arid climate (Köppen BSk) in August, defined by hot, dry days and significant diurnal temperature shifts. It is typically one of the warmest and driest times of the year, making it a peak period for summer conditions in the Treasure Valley.

Updated with grounded research as of 2026-11-10.

The short answer

August in Boise is characterized by hot, dry conditions with daytime temperatures frequently reaching into the 90s°F, paired with cool evenings. It remains one of the driest months of the year, with minimal rainfall, typical of the region's semi-arid environment.

Key facts

Average High Temperature
90°F - 91°F
Average Low Temperature
60°F - 61°F
Average Precipitation
Approximately 0.24 inches
Climate Normals Period
1991–2020

Temperature Patterns and Diurnal Variation

Boise experiences significant diurnal temperature variation in August, meaning the difference between daytime highs and nighttime lows is often substantial. While afternoons are consistently hot, the low humidity levels allow the air to cool rapidly after sunset, providing relief during the overnight hours.

  • Daytime highs typically hover around 90°F to 91°F.
  • Overnight lows generally settle between 60°F and 61°F.
  • The dry air facilitates rapid cooling once the sun sets, which is a hallmark of Idaho's high-desert climate.

Precipitation and Humidity

August is historically one of the driest months in the Boise area. Residents and local planners should expect very little precipitation, as the region's semi-arid climate creates conditions that are unfavorable for significant rainfall during the late summer months.

  • Average monthly precipitation is approximately 0.24 inches.
  • Humidity levels remain low, contributing to the 'dry heat' often associated with the Treasure Valley in late summer.

Planning Considerations

For those relocating to Boise or planning housing developments, understanding these climate patterns is essential for property management and landscape design. The combination of high heat and low precipitation influences everything from water usage requirements for landscaping to the importance of efficient cooling systems in residential construction.

  • Property owners often prioritize drought-tolerant landscaping (xeriscaping) to adapt to the dry summer climate.
  • Residential HVAC systems are heavily utilized in August, making home insulation and energy efficiency key considerations for buyers and renovators.

Common questions

Is August the hottest month in Boise?

While weather can vary from year to year, August is consistently among the hottest months in Boise, closely aligned with July in terms of average temperatures.

Does it rain often in Boise during August?

No, rainfall is very scarce in August. With an average of only 0.24 inches of precipitation, it is one of the driest months of the year for the region.

Related Idaho questions

  • What is the average annual precipitation in Boise?
  • How does Boise's winter climate compare to its summer climate?
  • Where can I find current, daily weather forecasts for Boise?

Sources and verification