San Jose Air Quality in May
Across 2019–2025, San Jose's May air quality had a median AQI of 47 (Good) over 217 monitored days in the San Jose-Sunnyvale-Santa Clara, CA area. 0.5% of May days (1 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 59.0% of days. The cleanest May on record here was 2023 (median AQI 39, 0 days above 100) and the worst was 2022 (median 44, 1 day above 100, peak AQI 112).
- Good: 63.6%
- Moderate: 35.9%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.0%
Extra Protection for San Jose Homes
Air quality in San Jose is moderate (AQI 53), 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 is the air in San Jose in May?
Good on a typical day: median AQI 47 across 2019–2025, with 0.5% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓63.6% of May days were Good (AQI 0–50), 35.9% Moderate (51–100).
- ✓1 day of 217 reached AQI 101+; the May peak was 112.
- ✓Best May: 2023; worst May: 2022.
Frequently asked questions
What is the air quality like in San Jose in May?▾
Across 2019–2025, the median daily AQI in San Jose in May was 47 (Good). 63.6% of days were Good, 35.9% Moderate, and 0.5% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in San Jose?▾
A typical May day in San Jose sits in the Good range (median AQI 47), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
Which pollutant causes San Jose's May air quality problems?▾
Ground-level ozone set the daily AQI on 59.0% of May days in San Jose. The highest May AQI recorded in 2019–2025 was 112 (Unhealthy for Sensitive Groups), in 2022.
San Jose May air quality, year by year
San Jose May air quality by year (San Jose-Sunnyvale-Santa Clara, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 45 | 0 | 61 | PM2.5 |
| 2020 | 31 | 47 | 0 | 84 | O3 |
| 2021 | 31 | 53 | 0 | 64 | PM2.5 |
| 2022worst | 31 | 44 | 1 | 112 | O3 |
| 2023cleanest | 31 | 39 | 0 | 81 | O3 |
| 2024 | 31 | 51 | 0 | 65 | PM2.5 |
| 2025 | 31 | 45 | 0 | 71 | O3 |
What May air means in San Jose
A typical May day in San Jose sits in the Good range (median AQI 47), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
May's median AQI of 47 is in line with San Jose's whole-year median of 50, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so San Jose runs in line with the national May norm; 0.5% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of San Jose's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Jose
The latest EPA AirNow observation puts San Jose's AQI at 53 (PM2.5). The figures above are multi-year month 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.