What Is the Air Quality in Idaho, Idaho?

Idaho, Idaho earns a C — air quality is fair, but not great. With a 5-year median AQI of 42, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.

Idaho, Idaho's 5-year median AQI of 42 is right around the national average of 41 across the 1,020 monitored U.S. cities tracked here. Within Idaho, Idaho, Idaho runs more polluted than the state average of 33 — local sources or geography are concentrating pollution above the state's typical reading.

For context within Idaho: Custer, Idaho currently holds the state's cleanest grade (A, AQI 8), while Valley, Idaho sits at the bottom (D, AQI 37).

Air quality in Idaho, Idaho has been getting worse over the past decade, with median AQI climbing by roughly 1.1 points per year. That bucks the national trend of broad improvement, and most often reflects either growing wildfire smoke exposure (particularly across the West) or rising local emissions from population and freight growth.

In 2015, Idaho, Idaho posted a median AQI of 27. By 2023 that figure was 44 — a rise of 17 AQI points dirtier across 9 years of EPA records.

Across the past five years, this area has logged 35 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 7 days per year. That is roughly typical for a U.S. metro, with most caution days clustered in summer (ozone) or wildfire season.

Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.