McHenry County, Illinois
Moderate air qualityGera US Air Health Index: 45.4/100 · National rank 406 of 458 · EPA AQS June 2026
What is the air quality in McHenry County, Illinois?
As of June 2026, McHenry County, Illinois has a Gera US Air Health Index of 45.4/100 (rank 406/458; moderate air quality). Annual mean PM2.5: 9.1 µg/m³; 8-hour ozone mean: 47.2 ppb; days with AQI > 100: 21. Source: EPA AQS AirData June 2026.
Air quality data — McHenry County (EPA AQS June 2026)
| Metric | Value | US Standard / Context |
|---|---|---|
| Annual mean PM2.5 | 9.1 µg/m³ | Above 9 µg/m³ NAAQS (2024) |
| Mean 8-hour ozone | 47.2 ppb | Within 70 ppb standard (2015) |
| Days with AQI > 100 | 21 days | Unhealthy for sensitive groups or worse |
| Maximum AQI recorded | 230 | During any day in 2023 |
| Median AQI (monitored days) | 49 | Typical daily AQI |
| GUSAHI composite | 45.4 / 100 | Higher = cleaner air |
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McHenry County, Illinois
National rank: 406 / 458 (by air quality, 1 = cleanest)
Gera US Air Health Index (GUSAHI)
45.4 / 100
Annual PM2.5
9.1 µg/m³
Above 9 µg/m³ std
Mean 8-hr Ozone
47.2 ppb
70 ppb standard
Days AQI > 100
21
in 2023
Source: EPA AQS AirData, June 2026 · Full county page →
Other counties in Illinois
Related health data on GeraClinic
Frequently asked questions
- What is the air quality like in McHenry County, Illinois?
- According to EPA AQS 2023 data, McHenry County, Illinois has a Gera US Air Health Index of 45.4 / 100 (rank 406 of 458 monitored counties; moderate air quality). Annual mean PM2.5 was 9.1 µg/m³, mean 8-hour ozone 47.2 ppb, with 21 days where the AQI exceeded 100. Source: EPA AQS AirData, June 2026.
- Is PM2.5 in McHenry County above the US health standard?
- The US EPA 2024 annual PM2.5 standard is 9 µg/m³. In 2023, McHenry County recorded an annual mean PM2.5 of 9.1 µg/m³, which is above the 9 µg/m³ standard. This figure is averaged from EPA AQS monitors operating in the county under the PM25 Annual 2012 standard.
- What is the ozone level in McHenry County?
- In 2023, McHenry County, Illinois had an annual mean 8-hour ozone daily maximum of 47.2 ppb. The US EPA 2015 ozone standard is 70 ppb (8-hour). This figure is averaged from AQS monitors in the county using the Ozone 8-hour 2015 standard. Source: EPA AQS AirData, June 2026.
- How many unhealthy air days did McHenry County have in 2023?
- In 2023, McHenry County had 21 days where the AQI exceeded 100 — covering the "Unhealthy for Sensitive Groups", "Unhealthy", "Very Unhealthy", and "Hazardous" AQI categories. An AQI above 100 indicates that the air may be unhealthy for sensitive groups; above 150 it is unhealthy for everyone. Source: EPA AQS annual_aqi_by_county_2023, June 2026.
- How can I check current air quality in McHenry County?
- For real-time AQI readings, visit AirNow.gov (airnow.gov) — the EPA's official current air quality portal. The GUSAHI index on GeraClinic reflects 2023 annual averages and is a longer-term health context measure, not a real-time reading. If you have respiratory conditions, a GeraClinic care navigator can help you assess your personal risk.
Concerned about air quality in McHenry County?
Poor air quality is associated with higher rates of respiratory and cardiovascular disease. A GeraClinic care navigator can help you understand what these EPA figures mean for your health, assess your individual risk, and connect you with specialist care — fully online.
Contains public sector information published by U.S. Environmental Protection Agency (EPA) and licensed under the U.S. Public Domain (federal government work, 17 U.S.C. § 105). Source: EPA AQS AirData — Annual AQI by County + Annual Concentration by Monitor, 2023 (June 2026, published 2023 (released 2024)).
Informational/educational only — not a substitute for professional medical advice; a clinician interprets results.