San Jose Air Quality in 2021
In 2021, San Jose's air quality (San Jose-Sunnyvale-Santa Clara, CA area) had a median daily AQI of 53 (Moderate) across 365 monitored days. 7 days (1.9%) reached Unhealthy for Sensitive Groups or worse, 144 were Good, and the year's peak AQI was 147 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 251 of those days. The cleanest month of 2021 was March (median AQI 49, 0 days above 100) and the worst was September (median 62, 2 days above 100, peak 101).
- Good: 39.5%
- Moderate: 58.6%
- Unhealthy for Sensitive Groups: 1.9%
- Unhealthy or worse: 0.0%
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How was San Jose's air quality in 2021?
Moderate on a typical day: median AQI 53, with 7 days above AQI 100 out of 365 monitored — the 6th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 147 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 251 days.
- ✓Cleanest month: March; worst: September.
Frequently asked questions
What was the average AQI in San Jose in 2021?▾
EPA's Air Quality System puts San Jose's (San Jose-Sunnyvale-Santa Clara, CA) median daily AQI for 2021 at 53, which is Moderate. 7 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 147.
Which month had the worst air quality in San Jose in 2021?▾
The cleanest month of 2021 was March (median AQI 49, 0 days above 100) and the worst was September (median 62, 2 days above 100, peak 101).
Was 2021 a good or bad year for San Jose's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 6th cleanest by days above AQI 100. 2021's median of 53 is above the area's typical annual median of 50.
San Jose month by month in 2021
San Jose air quality month by month, 2021 (San Jose-Sunnyvale-Santa Clara, CA, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 61 | 0 | 84 | PM2.5 |
| February | 28 | 51 | 0 | 76 | PM2.5 |
| Marchcleanest | 31 | 49 | 0 | 59 | PM2.5 |
| April | 30 | 56 | 0 | 71 | PM2.5 |
| May | 31 | 53 | 0 | 64 | PM2.5 |
| June | 30 | 44 | 1 | 129 | O3 |
| July | 31 | 53 | 0 | 87 | PM2.5 |
| August | 31 | 58 | 2 | 147 | PM2.5 |
| Septemberworst | 30 | 62 | 2 | 101 | PM2.5 |
| October | 31 | 48 | 2 | 129 | PM2.5 |
| November | 30 | 58 | 0 | 86 | PM2.5 |
| December | 31 | 49 | 0 | 93 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 6th cleanest by days above AQI 100.
2021's median of 53 is above the area's typical annual median of 50.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Jose
The latest EPA AirNow observation puts San Jose's AQI at 44 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current San Jose air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Jose-Sunnyvale-Santa Clara, CA), 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.