What Is the Air Quality in Mariposa, California?

Mariposa, California earns a C — air quality is fair, but not great. With a 5-year median AQI of 49, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.

Mariposa, California's 5-year median AQI of 49 is 8 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within California, Mariposa, California's air quality is roughly typical for the state, where the average city posts a 5-year median AQI of 49.

For context within California: Humboldt, California currently holds the state's cleanest grade (A, AQI 28), while Inyo, California sits at the bottom (F, AQI 57).

Air quality in Mariposa, California has been improving over the past decade, with median AQI dropping by roughly 0.4 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, Mariposa, California posted a median AQI of 53. By 2023 that figure was 47 — a drop of 6 AQI points cleaner across 10 years of EPA records.

Across the past five years, this area has logged 140 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 28 days per year, or roughly one every five to seven days. That is well above the national norm and explains the C grade.

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 ozone peaks in the afternoon on hot sunny days, plan outdoor exercise for early morning or after sunset on bad-air days.