Lewis and Clark County, Montana
Good air qualityGera US Air Health Index: 60.7/100 · National rank 127 of 458 · EPA AQS June 2026
What is the air quality in Lewis and Clark County, Montana?
As of June 2026, Lewis and Clark County, Montana has a Gera US Air Health Index of 60.7/100 (rank 127/458; good air quality). Annual mean PM2.5: 6.7 µg/m³; 8-hour ozone mean: 43.1 ppb; days with AQI > 100: 5. Source: EPA AQS AirData June 2026.
Air quality data — Lewis and Clark County (EPA AQS June 2026)
| Metric | Value | US Standard / Context |
|---|---|---|
| Annual mean PM2.5 | 6.7 µg/m³ | Within 9 µg/m³ NAAQS (2024) |
| Mean 8-hour ozone | 43.1 ppb | Within 70 ppb standard (2015) |
| Days with AQI > 100 | 5 days | Unhealthy for sensitive groups or worse |
| Maximum AQI recorded | 165 | During any day in 2023 |
| Median AQI (monitored days) | 45 | Typical daily AQI |
| GUSAHI composite | 60.7 / 100 | Higher = cleaner air |
Check another county's air quality
Compare any of the 458 included counties' GUSAHI, PM2.5, ozone, and AQI day counts.
Lewis and Clark County, Montana
National rank: 127 / 458 (by air quality, 1 = cleanest)
Gera US Air Health Index (GUSAHI)
60.7 / 100
Annual PM2.5
6.7 µg/m³
Within 9 µg/m³ std
Mean 8-hr Ozone
43.1 ppb
70 ppb standard
Days AQI > 100
5
in 2023
Source: EPA AQS AirData, June 2026 · Full county page →
Other counties in Montana
Related health data on GeraClinic
Frequently asked questions
- What is the air quality like in Lewis and Clark County, Montana?
- According to EPA AQS 2023 data, Lewis and Clark County, Montana has a Gera US Air Health Index of 60.7 / 100 (rank 127 of 458 monitored counties; good air quality). Annual mean PM2.5 was 6.7 µg/m³, mean 8-hour ozone 43.1 ppb, with 5 days where the AQI exceeded 100. Source: EPA AQS AirData, June 2026.
- Is PM2.5 in Lewis and Clark County above the US health standard?
- The US EPA 2024 annual PM2.5 standard is 9 µg/m³. In 2023, Lewis and Clark County recorded an annual mean PM2.5 of 6.7 µg/m³, which is below 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 Lewis and Clark County?
- In 2023, Lewis and Clark County, Montana had an annual mean 8-hour ozone daily maximum of 43.1 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 Lewis and Clark County have in 2023?
- In 2023, Lewis and Clark County had 5 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 Lewis and Clark 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 Lewis and Clark 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.