Modesto Air Quality in August
Across 2019–2025, Modesto's August air quality had a median AQI of 64 (Moderate) over 217 monitored days in the Modesto, CA area. 18.9% of August days (41 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 79.7% of days. The cleanest August on record here was 2025 (median AQI 50, 0 days above 100) and the worst was 2021 (median 97, 13 days above 100, peak AQI 166).
- Good: 28.6%
- Moderate: 52.5%
- Unhealthy for Sensitive Groups: 15.2%
- Unhealthy or worse: 3.7%
Extra Protection for Modesto Homes
Air quality in Modesto is moderate (AQI 63), with particle pollution 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 Modesto in August?
Moderate on a typical day: median AQI 64 across 2019–2025, with 18.9% of August days above AQI 100. Ground-level ozone is the main driver.
- ✓28.6% of August days were Good (AQI 0–50), 52.5% Moderate (51–100).
- ✓41 days of 217 reached AQI 101+; the August peak was 188.
- ✓Best August: 2025; worst August: 2021.
Frequently asked questions
What is the air quality like in Modesto in August?▾
Across 2019–2025, the median daily AQI in Modesto in August was 64 (Moderate). 28.6% of days were Good, 52.5% Moderate, and 18.9% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is August a good time for outdoor exercise in Modesto?▾
A typical August day in Modesto is Moderate (median AQI 64): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 5 of August days (18.9%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Modesto's August air quality problems?▾
Ground-level ozone set the daily AQI on 79.7% of August days in Modesto. The highest August AQI recorded in 2019–2025 was 188 (Unhealthy), in 2021.
Modesto August air quality, year by year
Modesto August air quality by year (Modesto, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 54 | 5 | 136 | O3 |
| 2020 | 31 | 74 | 11 | 188 | O3 |
| 2021worst | 31 | 97 | 13 | 166 | O3 |
| 2022 | 31 | 58 | 3 | 136 | O3 |
| 2023 | 31 | 64 | 3 | 119 | O3 |
| 2024 | 31 | 67 | 6 | 140 | O3 |
| 2025cleanest | 31 | 50 | 0 | 90 | O3 |
What August air means in Modesto
A typical August day in Modesto is Moderate (median AQI 64): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 5 of August days (18.9%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
August's median AQI of 64 is above Modesto's whole-year median of 54, making it one of the area's dirtier periods. Nationally, the median August AQI across every EPA metro area (104,152 metro-days, 2019–2025) is 45, so Modesto runs above the national August norm; 18.9% of its August days topped AQI 100 versus 3.5% nationally (above average).
August is part of Modesto's summer season (June, July, August); the summer page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Modesto
The latest EPA AirNow observation puts Modesto's AQI at 63 (PM10). The figures above are multi-year month statistics, not today's reading.
View current Modesto air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Modesto, 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.