Riverside Air Quality in Winter
Across 2019–2025, Riverside's winter (December–February) air quality had a median AQI of 65 (Moderate) over 632 monitored days in the Riverside-San Bernardino-Ontario, CA area. 8.8% of winter days (56 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 86.4% of days. The cleanest winter on record here was 2019 (median AQI 60, 4 days above 100) and the worst was 2025 (median 65, 12 days above 100, peak AQI 365).
- Good: 10.9%
- Moderate: 80.2%
- Unhealthy for Sensitive Groups: 6.3%
- Unhealthy or worse: 2.5%
Extra Protection for Riverside Homes
Air quality in Riverside is moderate (AQI 56), with fine particles (PM2.5) 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 Riverside in winter?
Moderate on a typical day: median AQI 65 across 2019–2025, with 8.8% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓10.9% of winter days were Good (AQI 0–50), 80.2% Moderate (51–100).
- ✓56 days of 632 reached AQI 101+; the winter peak was 409.
- ✓Cleanest month: January; worst month: December.
Frequently asked questions
What is the air quality like in Riverside in winter?▾
Across 2019–2025, the median daily AQI in Riverside in winter was 65 (Moderate). 10.9% of days were Good, 80.2% Moderate, and 8.8% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Riverside?▾
A typical winter day in Riverside is Moderate (median AQI 65): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of winter days (8.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Riverside's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 86.4% of winter days in Riverside. The highest winter AQI recorded in 2019–2025 was 409 (Hazardous), in 2025.
Riverside winter air quality, year by year
Riverside winter air quality by year (Riverside-San Bernardino-Ontario, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 90 | 60 | 4 | 121 | PM2.5 |
| 2020 | 91 | 69 | 9 | 207 | PM2.5 |
| 2021 | 90 | 70 | 10 | 187 | PM2.5 |
| 2022 | 90 | 65 | 4 | 409 | PM2.5 |
| 2023 | 90 | 59 | 6 | 177 | PM2.5 |
| 2024 | 91 | 65 | 11 | 157 | PM2.5 |
| 2025worst | 90 | 65 | 12 | 365 | PM2.5 |
What winter air means in Riverside
A typical winter day in Riverside is Moderate (median AQI 65): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of winter days (8.8%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Winter's median AQI of 65 is below Riverside's whole-year median of 89, making it one of the area's cleaner periods. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Riverside runs above the national Winter norm; 8.8% of its Winter days topped AQI 100 versus 0.6% nationally (above average).
Within the season, January is the cleanest month (median AQI 64, 6.9% of days above 100) and December the worst (median 68, 12.4% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Riverside
The latest EPA AirNow observation puts Riverside's AQI at 56 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current Riverside air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Riverside-San Bernardino-Ontario, 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.