What Is the Air Quality in Hamilton, Indiana?

Hamilton, Indiana earns a C — air quality is fair, but not great. With a 5-year median AQI of 45, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.

Hamilton, Indiana's 5-year median AQI of 45 is 4 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within Indiana, Hamilton, Indiana runs more polluted than the state average of 41 — local sources or geography are concentrating pollution above the state's typical reading.

For context within Indiana: Floyd, Indiana currently holds the state's cleanest grade (A, AQI 36), while Marion, Indiana sits at the bottom (C, AQI 57).

Air quality in Hamilton, Indiana has been improving over the past decade, with median AQI dropping by roughly 0.3 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.

In 2014, Hamilton, Indiana posted a median AQI of 48. By 2023 that figure was 46 — a drop of 2 AQI points cleaner across 10 years of EPA records.

Across the past five years, this area has logged just 12 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 2 days per year, or roughly one every other month. That is a low count by national standards.

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.