San Jose Air Quality in 2020
In 2020, San Jose's air quality (San Jose-Sunnyvale-Santa Clara, CA area) had a median daily AQI of 52 (Moderate) across 366 monitored days. 22 days (6.0%) reached Unhealthy for Sensitive Groups or worse, 169 were Good, and the year's peak AQI was 198 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 227 of those days. The cleanest month of 2020 was March (median AQI 39, 0 days above 100) and the worst was September (median 72, 9 days above 100, peak 198).
- Good: 46.2%
- Moderate: 47.8%
- Unhealthy for Sensitive Groups: 3.0%
- Unhealthy or worse: 3.0%
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How was San Jose's air quality in 2020?
Moderate on a typical day: median AQI 52, with 22 days above AQI 100 out of 366 monitored — the 7th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2020: 198 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 227 days.
- ✓Cleanest month: March; worst: September.
Frequently asked questions
What was the average AQI in San Jose in 2020?▾
EPA's Air Quality System puts San Jose's (San Jose-Sunnyvale-Santa Clara, CA) median daily AQI for 2020 at 52, which is Moderate. 22 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 198.
Which month had the worst air quality in San Jose in 2020?▾
The cleanest month of 2020 was March (median AQI 39, 0 days above 100) and the worst was September (median 72, 9 days above 100, peak 198).
Was 2020 a good or bad year for San Jose's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 7th cleanest by days above AQI 100 — the worst year on record here. 2020's median of 52 is in line with the area's typical annual median of 50.
San Jose month by month in 2020
San Jose air quality month by month, 2020 (San Jose-Sunnyvale-Santa Clara, CA, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 52 | 0 | 69 | PM2.5 |
| February | 29 | 52 | 0 | 69 | PM2.5 |
| Marchcleanest | 31 | 39 | 0 | 57 | O3 |
| April | 30 | 40 | 0 | 71 | O3 |
| May | 31 | 47 | 0 | 84 | O3 |
| June | 30 | 41 | 0 | 64 | O3 |
| July | 31 | 48 | 0 | 86 | PM2.5 |
| August | 31 | 69 | 9 | 172 | PM2.5 |
| Septemberworst | 30 | 72 | 9 | 198 | PM2.5 |
| October | 31 | 63 | 3 | 168 | PM2.5 |
| November | 30 | 58 | 0 | 93 | PM2.5 |
| December | 31 | 60 | 1 | 105 | PM2.5 |
How 2020 compares
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 7th cleanest by days above AQI 100 — the worst year on record here.
2020's median of 52 is in line with 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.