Idaho local data guide
Average Annual Precipitation in Boise
Boise, Idaho, maintains a semi-arid climate characterized by an official average annual precipitation of 11.51 inches, as measured by the 1991–2020 climate normals from the National Weather Service.
Updated with grounded research as of 2026-07-21.
The short answer
Boise experiences a semi-arid climate with an official average annual precipitation of 11.51 inches. This measurement is derived from the 1991–2020 climate normals recorded at the Boise Air Terminal and serves as the baseline for understanding the region's typical moisture levels throughout the year.
Key facts
- Average Annual Precipitation
- 11.51 inches
Understanding Boise's Climate Classification
The National Weather Service classifies the Boise area as having a semi-arid climate. This designation reflects the region's generally dry conditions, where potential evapotranspiration often exceeds the total annual precipitation received.
Seasonal Precipitation Patterns
Precipitation in Boise is not distributed evenly throughout the year. The majority of the city's annual moisture occurs during the cooler months, specifically between November and May, while the summer months are typically quite dry.
Localized Variability
While 11.51 inches is the official baseline, it is important for residents to recognize that geography plays a significant role in local weather. Factors such as elevation changes between the Boise foothills and the valley floor can result in variations in total annual rainfall and snowfall compared to the airport measurements.
Common questions
Does Boise have a rainy season?
Boise does not have a formal 'rainy season' in the tropical sense, but it does experience a distinct increase in precipitation frequency during the winter and spring months, specifically from November through May.
How does this data impact local planning?
For those involved in landscaping, housing development, or water management, the 11.51-inch average underscores the importance of water conservation and the selection of drought-tolerant vegetation, as the region remains naturally arid.
Related Idaho questions
- What is the average snowfall in Boise?
- How does Boise's climate compare to other cities in Idaho?
Sources and verification
- Review National Weather Service climate data (weather.gov)