Idaho local data guide
Annual Precipitation in Boise, Idaho
Boise, Idaho, is situated in a semi-arid climate, receiving an average annual precipitation of 11.51 inches based on official U.S. Climate Normals (1991–2020).
Updated with grounded research as of 2026-08-25.
The short answer
According to the National Oceanic and Atmospheric Administration (NOAA), the Boise area receives an average of 11.51 inches of precipitation annually. This figure is based on the 1991–2020 U.S. Climate Normals, which serve as the standard 30-year average for comparing current weather patterns against long-term trends.
Key facts
- Annual Precipitation Normal (1991–2020)
- 11.51 inches
Understanding Climate Normals
Climate 'normals' are not predictions of what will happen in any single year; rather, they are 30-year averages used by meteorologists to provide context for daily, monthly, and seasonal weather. The 11.51-inch figure represents the combined total of rainfall and the liquid equivalent of snowfall measured at the official reporting station for the Boise area.
The Semi-Arid Landscape
Boise’s location contributes to its dry climate. Because the city sits in the rain shadow of the mountains to its west and south, it receives significantly less moisture than many other parts of the United States. This semi-arid environment is characterized by dry summers and moderate winter precipitation, which influences local landscape design, water usage requirements, and regional housing development strategies.
Geographic Variability
While the official 11.51-inch statistic is the benchmark for the Boise area, local precipitation levels can vary significantly across the Treasure Valley. Factors such as elevation and proximity to the foothills can lead to microclimates where specific neighborhoods experience slightly higher or lower precipitation levels than those recorded at the official airport weather station.
Common questions
How does Boise's precipitation compare to the national average?
Boise is significantly drier than the national average for the United States, which typically sees upwards of 30 inches of precipitation annually. Its semi-arid classification means residents should plan for irrigation needs and dry climate living.
Does this 11.51-inch figure include snowfall?
Yes. This figure is the total annual precipitation, which includes rainfall and the water-equivalent of any snow, sleet, or hail that falls throughout the year.
Does precipitation vary between Boise and nearby cities like Nampa or Meridian?
While the entire Treasure Valley is semi-arid, there can be minor variations in precipitation due to subtle changes in elevation and local topography across Ada and Canyon counties. However, most cities in the valley share a generally dry climate profile.
Related Idaho questions
- What is the average annual snowfall in Boise?
- How to manage water usage for landscaping in Idaho's semi-arid climate?
- Current drought conditions and water management resources in the Treasure Valley.
Sources and verification
- National Weather Service: Boise Climate Data (weather.gov)
- NOAA: U.S. Climate Normals Overview (ncei.noaa.gov)