Modesto, California Air Quality
Modesto air quality today — the AQI, the main pollutant, and whether it’s safe to exercise outside right now
Modesto, CA · Air quality right now
The air quality index in Modesto, CA is 57 (Moderate) right now — acceptable for most people.
Is it safe to be outside in Modesto today?
AQI 57 Yes — air quality is Moderate
Fine for most; unusually sensitive people can take it easy.Main pollutant: PM2.5Observed 1:00 AM PDT
Pollutants right now
- PM2.512 µg/m³Main pollutantfine particles — smoke, exhaust, soot
- PM1027 µg/m³coarse particles — dust, pollen, ash
- Ozone29 µg/m³smog — builds on hot, sunny days
- NO₂19 µg/m³nitrogen dioxide — traffic, combustion
ExerciseOK to run for most; sensitive athletes can ease the intensity.
How to read Modesto’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 Modesto
Across the EPA’s county records from 2020 to 2025, Modesto’s cleanest year was 2025 (median AQI 51) and its most polluted was 2021 (median AQI 61); the typical (median) day has trended cleaner since 2020.
| Year | Median AQI | Unhealthy+ | Main pollutant | USG | Moderate | Good |
|---|---|---|---|---|---|---|
| 2020 | 60 | 16 | PM2.5 | 21 | 198 | 131 |
| 2021 | 61 | 5 | PM2.5 | 42 | 234 | 84 |
| 2022 | 57 | 1 | PM2.5 | 22 | 234 | 108 |
| 2023 | 54 | 0 | Ozone | 23 | 176 | 166 |
| 2024 | 53 | 0 | Ozone | 38 | 162 | 166 |
| 2025 | 51 | 0 | Ozone | 3 | 180 | 182 |
“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, 2020–2025.
Frequently asked
- What was the worst year for air quality in Modesto?
- In the EPA's 2020–2025 county records, 2021 had the most days above AQI 100: 47 days (42 Unhealthy for Sensitive Groups, 5 Unhealthy or worse). It also had the highest median AQI, 61.
- How many unhealthy air days does Modesto have?
- Across 2020–2025, 8% of the days reported for Modesto's county had an AQI above 100 (171 of 2192), about 29 days a year. 2025 had 3 days.
- What's the main air pollutant in Modesto?
- PM2.5 drove Modesto's county AQI on the most days in 3 of 6 years (2020–2025); Ozone in 2023, 2024, 2025.