Riverside Air Quality in May
Across 2019–2025, Riverside's May air quality had a median AQI of 105 (Unhealthy for Sensitive Groups) over 217 monitored days in the Riverside-San Bernardino-Ontario, CA area. 57.6% of May days (125 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 79.3% of days. The cleanest May on record here was 2019 (median AQI 77, 5 days above 100) and the worst was 2022 (median 122, 24 days above 100, peak AQI 1683).
- Good: 2.3%
- Moderate: 40.1%
- Unhealthy for Sensitive Groups: 38.2%
- Unhealthy or worse: 19.4%
Extra Protection for Riverside Homes
Air quality in Riverside is moderate (AQI 58), 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 May?
Unhealthy for Sensitive Groups on a typical day: median AQI 105 across 2019–2025, with 57.6% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓2.3% of May days were Good (AQI 0–50), 40.1% Moderate (51–100).
- ✓125 days of 217 reached AQI 101+; the May peak was 1683.
- ✓Best May: 2019; worst May: 2022.
Frequently asked questions
What is the air quality like in Riverside in May?▾
Across 2019–2025, the median daily AQI in Riverside in May was 105 (Unhealthy for Sensitive Groups). 2.3% of days were Good, 40.1% Moderate, and 57.6% 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 Riverside?▾
A typical May day in Riverside is already Unhealthy for Sensitive Groups (median AQI 105): people with asthma or heart disease, children and older adults should reduce prolonged outdoor exertion on most days, and about 58% of May days (57.6%) were at that level or worse.
Which pollutant causes Riverside's May air quality problems?▾
Ground-level ozone set the daily AQI on 79.3% of May days in Riverside. The highest May AQI recorded in 2019–2025 was 1683 (Hazardous), in 2022.
Riverside May air quality, year by year
Riverside May 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 | 31 | 77 | 5 | 147 | O3 |
| 2020 | 31 | 133 | 22 | 212 | O3 |
| 2021 | 31 | 115 | 23 | 329 | O3 |
| 2022worst | 31 | 122 | 24 | 1683 | O3 |
| 2023 | 31 | 105 | 17 | 230 | O3 |
| 2024 | 31 | 100 | 15 | 169 | O3 |
| 2025 | 31 | 108 | 19 | 169 | O3 |
What May air means in Riverside
A typical May day in Riverside is already Unhealthy for Sensitive Groups (median AQI 105): people with asthma or heart disease, children and older adults should reduce prolonged outdoor exertion on most days, and about 58% of May days (57.6%) were at that level or worse.
May's median AQI of 105 is above Riverside's whole-year median of 89, making it one of the area's dirtier periods. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Riverside runs above the national May norm; 57.6% of its May days topped AQI 100 versus 1.3% nationally (above average).
May is part of Riverside's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Riverside
The latest EPA AirNow observation puts Riverside's AQI at 58 (PM2.5). The figures above are multi-year month 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.