What Is the Air Quality in Humboldt, California?

Humboldt, California earns an A — it is among the cleanest U.S. cities tracked by EPA monitoring, with median AQI averaging just 28 over the past five years. Days in the "Good" category dominate the calendar; air-quality alerts are rare.

Humboldt, California's 5-year median AQI of 28 is 13 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within California, Humboldt, California runs cleaner than the state average of 49 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.

For context within California: Napa, California currently holds the state's cleanest grade (B, AQI 39), while Inyo, California sits at the bottom (F, AQI 57).

Air quality in Humboldt, California has been improving over the past decade, with median AQI dropping by roughly 2.3 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, Humboldt, California posted a median AQI of 53. By 2023 that figure was 32 — a drop of 21 AQI points cleaner across 10 years of EPA records.

Across the past five years, this area has logged just 15 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 3 days per year, or roughly one every other month. That is a low count by national standards.

For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire season. Because ozone peaks in the afternoon on hot sunny days, plan outdoor exercise for early morning or after sunset on bad-air days.