San Francisco Air Quality in Spring
Across 2019–2025, San Francisco's spring (March–May) air quality had a median AQI of 48 (Good) over 581 monitored days in the San Francisco-Oakland-Hayward, CA area. 0.3% of spring days (2 of 581) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 75.6% of days. The cleanest spring on record here was 2025 (median AQI 29, 0 days above 100) and the worst was 2023 (median 49, 1 day above 100, peak AQI 101).
- Good: 53.9%
- Moderate: 45.8%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 0.0%
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How is the air in San Francisco in spring?
Good on a typical day: median AQI 48 across 2019–2025, with 0.3% of spring days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓53.9% of spring days were Good (AQI 0–50), 45.8% Moderate (51–100).
- ✓2 days of 581 reached AQI 101+; the spring peak was 105.
- ✓Cleanest month: March; worst month: May.
Frequently asked questions
What is the air quality like in San Francisco in spring?▾
Across 2019–2025, the median daily AQI in San Francisco in spring was 48 (Good). 53.9% of days were Good, 45.8% Moderate, and 0.3% reached Unhealthy for Sensitive Groups or worse, based on 581 monitored days in EPA's Air Quality System.
Is spring a good time for outdoor exercise in San Francisco?▾
A typical spring day in San Francisco sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Which pollutant causes San Francisco's spring air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 75.6% of spring days in San Francisco. The highest spring AQI recorded in 2019–2025 was 105 (Unhealthy for Sensitive Groups), in 2023.
San Francisco spring air quality, year by year
San Francisco spring air quality by year (San Francisco-Oakland-Hayward, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 92 | 47 | 0 | 74 | PM2.5 |
| 2020 | 92 | 43 | 0 | 93 | PM2.5 |
| 2021 | 92 | 55 | 0 | 84 | PM2.5 |
| 2022 | 92 | 49 | 1 | 105 | PM2.5 |
| 2023worst | 92 | 49 | 1 | 101 | PM2.5 |
| 2024 | 92 | 50 | 0 | 73 | PM2.5 |
| 2025cleanest | 29 | 29 | 0 | 62 | PM2.5 |
What spring air means in San Francisco
A typical spring day in San Francisco sits in the Good range (median AQI 48), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of spring days reached AQI 101+ in 2019–2025.
Spring's median AQI of 48 is below San Francisco's whole-year median of 53, making it one of the area's cleaner periods. Nationally, the median Spring AQI across every EPA metro area (307,196 metro-days, 2019–2025) is 43, so San Francisco runs above the national Spring norm; 0.3% of its Spring days topped AQI 100 versus 0.8% nationally (about the same).
Within the season, March is the cleanest month (median AQI 43, 0.0% of days above 100) and May the worst (median 53, 0.5% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Francisco
The latest EPA AirNow observation puts San Francisco's AQI at 36 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current San Francisco air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Francisco-Oakland-Hayward, 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.