Boise Air Quality in 2021
In 2021, Boise's air quality (Boise City, ID area) had a median daily AQI of 54 (Moderate) across 365 monitored days. 20 days (5.5%) reached Unhealthy for Sensitive Groups or worse, 131 were Good, and the year's peak AQI was 173 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 248 of those days. The cleanest month of 2021 was May (median AQI 44, 0 days above 100) and the worst was July (median 80, 8 days above 100, peak 136).
- Good: 35.9%
- Moderate: 58.6%
- Unhealthy for Sensitive Groups: 4.4%
- Unhealthy or worse: 1.1%
Extra Protection for Boise Homes
Air quality in Boise is moderate (AQI 59), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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How was Boise's air quality in 2021?
Moderate on a typical day: median AQI 54, with 20 days above AQI 100 out of 365 monitored — the 5th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 173 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 248 days.
- ✓Cleanest month: May; worst: July.
Frequently asked questions
What was the average AQI in Boise in 2021?▾
EPA's Air Quality System puts Boise's (Boise City, ID) median daily AQI for 2021 at 54, which is Moderate. 20 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 173.
Which month had the worst air quality in Boise in 2021?▾
The cleanest month of 2021 was May (median AQI 44, 0 days above 100) and the worst was July (median 80, 8 days above 100, peak 136).
Was 2021 a good or bad year for Boise's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 5th cleanest by days above AQI 100. 2021's median of 54 is in line with the area's typical annual median of 54.
Boise month by month in 2021
Boise air quality month by month, 2021 (Boise City, ID, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 60 | 0 | 80 | PM2.5 |
| February | 28 | 52 | 0 | 61 | PM2.5 |
| March | 31 | 51 | 0 | 69 | PM2.5 |
| April | 30 | 46 | 0 | 61 | PM2.5 |
| Maycleanest | 31 | 44 | 0 | 69 | O3 |
| June | 30 | 49 | 0 | 80 | O3 |
| Julyworst | 31 | 80 | 8 | 136 | O3 |
| August | 31 | 71 | 6 | 173 | PM2.5 |
| September | 30 | 58 | 6 | 153 | PM2.5 |
| October | 31 | 45 | 0 | 66 | PM2.5 |
| November | 30 | 58 | 0 | 84 | PM2.5 |
| December | 31 | 58 | 0 | 93 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 5th cleanest by days above AQI 100.
2021's median of 54 is in line with the area's typical annual median of 54.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Boise
The latest EPA AirNow observation puts Boise's AQI at 59 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Boise air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Boise City, ID), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.