Modesto Air Quality in Summer
Across 2019–2025, Modesto's summer (June–August) air quality had a median AQI of 63 (Moderate) over 644 monitored days in the Modesto, CA area. 15.1% of summer days (97 of 644) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 85.6% of days. The cleanest summer on record here was 2025 (median AQI 51, 1 day above 100) and the worst was 2021 (median 81, 27 days above 100, peak AQI 172).
- Good: 32.3%
- Moderate: 52.6%
- Unhealthy for Sensitive Groups: 13.7%
- Unhealthy or worse: 1.4%
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 summer?
Moderate on a typical day: median AQI 63 across 2019–2025, with 15.1% of summer days above AQI 100. Ground-level ozone is the main driver.
- ✓32.3% of summer days were Good (AQI 0–50), 52.6% Moderate (51–100).
- ✓97 days of 644 reached AQI 101+; the summer peak was 188.
- ✓Cleanest month: June; worst month: July.
Frequently asked questions
What is the air quality like in Modesto in summer?▾
Across 2019–2025, the median daily AQI in Modesto in summer was 63 (Moderate). 32.3% of days were Good, 52.6% Moderate, and 15.1% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is summer a good time for outdoor exercise in Modesto?▾
A typical summer day in Modesto is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of summer days (15.1%) 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 summer air quality problems?▾
Ground-level ozone set the daily AQI on 85.6% of summer days in Modesto. The highest summer AQI recorded in 2019–2025 was 188 (Unhealthy), in 2021.
Modesto summer air quality, year by year
Modesto summer air quality by year (Modesto, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 92 | 53 | 12 | 143 | O3 |
| 2020 | 92 | 61 | 12 | 188 | O3 |
| 2021worst | 92 | 81 | 27 | 172 | O3 |
| 2022 | 92 | 58 | 6 | 136 | O3 |
| 2023 | 92 | 61 | 14 | 126 | O3 |
| 2024 | 92 | 77 | 25 | 147 | O3 |
| 2025cleanest | 92 | 51 | 1 | 115 | O3 |
What summer air means in Modesto
A typical summer day in Modesto is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of summer days (15.1%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Summer's median AQI of 63 is above Modesto's whole-year median of 54, making it one of the area's dirtier periods. Nationally, the median Summer AQI across every EPA metro area (308,645 metro-days, 2019–2025) is 46, so Modesto runs above the national Summer norm; 15.1% of its Summer days topped AQI 100 versus 3.6% nationally (above average).
Within the season, June is the cleanest month (median AQI 53, 6.7% of days above 100) and July the worst (median 71, 19.4% above 100).
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 season 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.