Modesto Air Quality in May
Across 2019–2025, Modesto's May air quality had a median AQI of 49 (Good) over 217 monitored days in the Modesto, CA area. 2.3% of May days (5 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 73.7% of days. The cleanest May on record here was 2019 (median AQI 46, 0 days above 100) and the worst was 2021 (median 52, 2 days above 100, peak AQI 115).
- Good: 54.8%
- Moderate: 42.9%
- Unhealthy for Sensitive Groups: 2.3%
- Unhealthy or worse: 0.0%
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 May?
Good on a typical day: median AQI 49 across 2019–2025, with 2.3% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓54.8% of May days were Good (AQI 0–50), 42.9% Moderate (51–100).
- ✓5 days of 217 reached AQI 101+; the May peak was 115.
- ✓Best May: 2019; worst May: 2021.
Frequently asked questions
What is the air quality like in Modesto in May?▾
Across 2019–2025, the median daily AQI in Modesto in May was 49 (Good). 54.8% of days were Good, 42.9% Moderate, and 2.3% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Modesto?▾
A typical May day in Modesto sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 43 of May days (2.3%) reached AQI 101+ in 2019–2025.
Which pollutant causes Modesto's May air quality problems?▾
Ground-level ozone set the daily AQI on 73.7% of May days in Modesto. The highest May AQI recorded in 2019–2025 was 115 (Unhealthy for Sensitive Groups), in 2021.
Modesto May air quality, year by year
Modesto May air quality by year (Modesto, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 31 | 46 | 0 | 77 | O3 |
| 2020 | 31 | 45 | 1 | 105 | O3 |
| 2021worst | 31 | 52 | 2 | 115 | PM2.5 |
| 2022 | 31 | 54 | 1 | 114 | PM2.5 |
| 2023 | 31 | 46 | 0 | 87 | O3 |
| 2024 | 31 | 50 | 0 | 87 | O3 |
| 2025 | 31 | 49 | 1 | 105 | O3 |
What May air means in Modesto
A typical May day in Modesto sits in the Good range (median AQI 49), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 43 of May days (2.3%) reached AQI 101+ in 2019–2025.
May's median AQI of 49 is below Modesto's whole-year median of 54, making it one of the area's cleaner periods. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Modesto runs above the national May norm; 2.3% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Modesto's spring season (March, April, May); the spring 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.