Fremont, California Air Quality
Fremont air quality today — the AQI, the main pollutant, and whether it’s safe to exercise outside right now
Fremont, CA · Air quality right now
The air quality index in Fremont, CA is 52 (Moderate) right now — acceptable for most people.
Is it safe to be outside in Fremont today?
AQI 52 Yes — air quality is Moderate
Fine for most; unusually sensitive people can take it easy.Main pollutant: PM2.5Observed 12:00 AM PDT
Pollutants right now
- PM2.59.5 µg/m³Main pollutantfine particles — smoke, exhaust, soot
- PM1013 µg/m³coarse particles — dust, pollen, ash
- Ozone47 µg/m³smog — builds on hot, sunny days
- NO₂14 µg/m³nitrogen dioxide — traffic, combustion
ExerciseOK to run for most; sensitive athletes can ease the intensity.
How to read Fremont’s air quality
Guides: The AQI Scale, Explained · Air Quality Alerts, Decoded · How to Read a Wildfire Smoke Map · Why Wildfire Smoke Travels 1,000 Miles.
Air quality over time in Fremont
Across the EPA’s county records from 2020 to 2024, Fremont’s cleanest year was 2023 (median AQI 48) and its most polluted was 2021 (median AQI 53); the typical (median) day has trended cleaner since 2020.
| Year | Median AQI | Unhealthy+ | Main pollutant | USG | Moderate | Good |
|---|---|---|---|---|---|---|
| 2020 | 52 | 12 | PM2.5 | 8 | 177 | 169 |
| 2021 | 53 | 1 | PM2.5 | 9 | 200 | 155 |
| 2022 | 49 | 0 | PM2.5 | 5 | 175 | 185 |
| 2023 | 48 | 0 | PM2.5 | 13 | 155 | 197 |
| 2024 | 49 | 0 | PM2.5 | 1 | 171 | 194 |
“USG” is Unhealthy for Sensitive Groups (AQI 101–150); “Unhealthy+” combines the Unhealthy, Very Unhealthy, and Hazardous days. In 2024 the EPA tightened the annual fine-particle (PM2.5) standard to 9 µg/m³ from the previous 12 µg/m³, so counties near the old limit read worse against the new one. Source: EPA AQS annual summaries, 2020–2024.
Frequently asked
- What was the worst year for air quality in Fremont?
- In the EPA's 2020–2024 county records, 2020 had the most days above AQI 100: 20 days (8 Unhealthy for Sensitive Groups, 12 Unhealthy or worse). The highest median AQI came in 2021 (53; 2020's was 52).
- How many unhealthy air days does Fremont have?
- Across 2020–2024, 3% of the days reported for Fremont's county had an AQI above 100 (49 of 1827), about 10 days a year. 2024 had 1 day.
- What's the main air pollutant in Fremont?
- PM2.5: it drove Fremont's county AQI on the most days in every year of the EPA's 2020–2024 records.