Modesto Air Quality in January
Across 2019–2025, Modesto's January air quality had a median AQI of 64 (Moderate) over 217 monitored days in the Modesto, CA area. 6.0% of January days (13 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 91.7% of days. The cleanest January on record here was 2023 (median AQI 39, 0 days above 100) and the worst was 2019 (median 72, 6 days above 100, peak AQI 120).
- Good: 23.0%
- Moderate: 71.0%
- Unhealthy for Sensitive Groups: 6.0%
- 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
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Modesto in January?
Moderate on a typical day: median AQI 64 across 2019–2025, with 6.0% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓23.0% of January days were Good (AQI 0–50), 71.0% Moderate (51–100).
- ✓13 days of 217 reached AQI 101+; the January peak was 120.
- ✓Best January: 2023; worst January: 2019.
Frequently asked questions
What is the air quality like in Modesto in January?▾
Across 2019–2025, the median daily AQI in Modesto in January was 64 (Moderate). 23.0% of days were Good, 71.0% Moderate, and 6.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in Modesto?▾
A typical January 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 17 of January days (6.0%) 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 January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 91.7% of January days in Modesto. The highest January AQI recorded in 2019–2025 was 120 (Unhealthy for Sensitive Groups), in 2019.
Modesto January air quality, year by year
Modesto January air quality by year (Modesto, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 31 | 72 | 6 | 120 | PM2.5 |
| 2020 | 31 | 64 | 0 | 91 | PM2.5 |
| 2021 | 31 | 68 | 3 | 120 | PM2.5 |
| 2022 | 31 | 88 | 4 | 111 | PM2.5 |
| 2023cleanest | 31 | 39 | 0 | 87 | PM2.5 |
| 2024 | 31 | 55 | 0 | 81 | PM2.5 |
| 2025 | 31 | 65 | 0 | 87 | PM2.5 |
What January air means in Modesto
A typical January 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 17 of January days (6.0%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
January'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 January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Modesto runs above the national January norm; 6.0% of its January days topped AQI 100 versus 0.7% nationally (above average).
January is part of Modesto's winter season (December, January, February); the winter 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.