AIR QUALITY CA

Air Quality in Gilroy, CA: Good (41 AQI)

AQI 41 · Good · PM2.5 · Updated 2026-07-18

Gilroy's air quality is good. Air pollution poses little or no risk.

Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-07-18

Average AQI

Good

AQI Category

Wildfire Risk

Mold Score

ZIP Codes

What is AQI?

The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Gilroy's average AQI of 41 falls in the "Good" range.

How do wildfires affect air quality?

Wildfire smoke contains fine particulate matter (PM2.5) that can travel hundreds of miles and dramatically spike AQI readings. During fire season, even cities far from active fires can experience unhealthy air. HEPA air purifiers (rated for PM2.5) are the most effective indoor protection. Check AirNow.gov for real-time conditions during fire season.

Air Quality by ZIP Code in Gilroy

AQI varies across Gilroy's 2 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
95020	41	Good	35	33	View report →
95021	41	Good	35	21	View report →

Air Quality Overview

Gilroy, California has good air quality with an average AQI of 41. This means air pollution poses little or no risk. The dominant pollutant measured is PM2.5.

The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."

Dominant Pollutant: PM2.5

PM2.5 (fine particulate matter) consists of particles smaller than 2.5 micrometers - about 30 times thinner than a human hair. These particles can penetrate deep into the lungs and enter the bloodstream.

Health effects of PM2.5 exposure:

Short-term: coughing, shortness of breath, aggravated asthma
Long-term: reduced lung function, cardiovascular disease, premature death
Most vulnerable: children, elderly, people with heart or lung disease

Common sources in urban areas: vehicle exhaust, construction dust, industrial emissions, wildfire smoke, residential wood burning.

Air Quality by ZIP Code in Gilroy

AQI varies across Gilroy's 2 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

ZIP Code	AQI	Category	Wildfire Risk	Mold Score
95020	41	Good	35	33
95021	41	Good	35	21

Wildfire Smoke Risk

Gilroy has an elevated wildfire smoke risk with an average smoke risk score of 35 (scale 0-100). There have been 28 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	35
Max smoke risk score	35
Fires within 100 km	28
High-risk ZIP codes	0

Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.

Indoor Mold Risk

Gilroy has an average mold risk score of 27 out of 100.

Factor	Value
Mold risk score	27/100
Average humidity	57% RH
High-risk ZIPs	0
Peak season	winter high

Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.

Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.

Health Recommendations

With good air quality (AQI 41), Gilroy residents can enjoy outdoor activities without significant restrictions. General tips:

Monitor AQI during wildfire season for temporary spikes
Use HEPA air purifiers indoors if you have respiratory conditions
Maintain indoor humidity between 30-50% to prevent mold

Gilroy vs. Nearby California Cities

How Gilroy's air quality compares to nearby cities:

City	AQI	Category	Population
Gilroy	41	Good	67,945
Union City	44	Good	68,141
Brentwood	49	Good	68,160
San Clemente	44	Good	67,298

ZIP Codes in Gilroy

Gilroy covers 2 ZIP codes. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.

Data Sources

Air quality: EPA AirNow - real-time and historical AQI data
Wildfire risk: FEMA National Risk Index
Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
Monthly AQI: EPA Air Quality Statistics

Updated daily.

Frequently Asked Questions

Is the air safe to breathe in Gilroy?

Yes - Gilroy's average AQI is 41 (Good). Air pollution poses little or no risk for the general population.

How many unhealthy air days does Gilroy have?

Gilroy has zero recorded unhealthy air quality days, which is excellent. Air quality can still vary seasonally due to wildfire smoke, pollen, or industrial activity.

What is the AQI in Gilroy?

The average Air Quality Index (AQI) in Gilroy is 41, categorized as Good. The primary pollutant is PM2.5. AQI ranges from 0-500, where 0-50 is Good, 51-100 Moderate, 101-150 Unhealthy for Sensitive Groups, and 151+ Unhealthy.

What is the wildfire risk in Gilroy?

Gilroy has a wildfire risk score of 35 out of 100. Moderate wildfire risk means smoke events are possible. Having a HEPA air purifier available is recommended.

Is mold a concern in Gilroy?

Gilroy has a mold risk score of 27 out of 100, based on humidity, precipitation, and temperature data. Maintain good ventilation and address any water intrusion promptly to prevent mold growth.

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