Lemhi, Idaho Air Quality
Lemhi County, Idaho (ID)
↓ Improvingover 10 years
How Lemhi, Idaho Air Quality Compares
Lemhi, Idaho's median AQI of 32is 22% better than the national average of 41. Air quality has improved by 20 AQI points over the past decade. Residents experience an average of 13 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Lemhi, Idaho Air Quality: The Full Picture
Lemhi, Idaho (Lemhi County) holds an AirHistory Air Quality Grade of B (good, scoring 69 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 20 points between 2014 (52) and 2023 (32), and the five-year median now sits at 40 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 363 of 363 monitored days (100% of the year), making it the controlling pollutant for the B grade. The single worst reading logged that year hit an AQI of 119 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 63.
In 2023, Lemhi County recorded 251 "Good" air days (69% of the 363 days with valid AQI data), 110 "Moderate" days, and 2 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 67 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 13 per year.
The decade-long trend is improving: median AQI has been dropping by roughly 1.39 points per year. The cleanest year in the record was 2019 (median AQI 31), and the most polluted was 2014 (median AQI 52). Because the data come straight from federally certified EPA monitors, these figures track the Idaho county the monitors physically sit in rather than a city boundary.
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10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). This area has seen measurable air quality improvement over the decade.
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 32 | 63 | 119 | 251 | 110 | 2 | PM2.5 |
| 2022 | 44 | 92 | 212 | 199 | 136 | 30 | PM2.5 |
| 2021 | 47 | 83 | 172 | 188 | 157 | 20 | PM2.5 |
| 2020 | 46 | 80 | 168 | 194 | 160 | 11 | PM2.5 |
| 2019 | 31 | 72 | 133 | 237 | 119 | 4 | PM2.5 |
| 2018 | 38 | 74 | 121 | 225 | 132 | 3 | PM2.5 |
| 2017 | 37 | 98 | 193 | 214 | 113 | 31 | PM2.5 |
| 2016 | 51 | 97 | 160 | 182 | 153 | 29 | PM2.5 |
| 2015 | 51 | 91 | 267 | 176 | 154 | 25 | PM2.5 |
| 2014 | 52 | 83 | 157 | 171 | 160 | 17 | PM2.5 |
What This Means for Lemhi County Residents
Lemhi, Idaho has received an Air Quality Grade of B (69/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 32 falls in the "Good" range.
Encouragingly, air quality here has been improving, with the median AQI dropping by 20 points over the monitoring period. This trend suggests continued investment in emission controls and cleaner energy.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 13 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
Related Cities in Idaho
Frequently Asked Questions
Lemhi, Idaho has a current median AQI of 32, which falls in the "Good" range. The area has received an Air Quality Grade of B (69/100) based on 10 years of EPA monitoring data.
Air quality in Lemhi, Idaho is improving over the past decade. The median AQI has changed by -20 points from 2014 to 2023.
Lemhi, Idaho averages 13 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Lemhi, Idaho is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Lemhi County area.
Lemhi, Idaho averages 13 unhealthy air days per year. Asthma patients should monitor daily AQI readings and limit outdoor activity when AQI exceeds 100. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 32 (Good), outdoor exercise in Lemhi, Idaho is generally safe year-round. Lemhi, Idaho averages 13 days per year when athletes should move workouts indoors.