Median AQI
55
Moderate
Arizona · County air quality · 2025
Pima County, Arizona
Median AQI 55 (Moderate). 37.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 55
- Median AQI
- 37.0%
- Good-air days
- 5
- Unhealthy days
- 2%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Pima County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 55 with 37.0% of 273 monitored days in the Good band, driven mainly by PM10.
- 55
- median AQI · Moderate
- 37.0%
- days rated Good
- PM10
- main pollutant
- 2%
- cleaner than US counties
5 days reached Unhealthy or worse; the worst single reading hit AQI 357.
Data updated July 2026
- Good · 101 d · 37.0%
- Moderate · 165 d · 60.4%
- USG · 2 d · 0.7%
- Unhealthy · 3 d · 1.1%
- Very Unhealthy · 1 d · 0.4%
- Hazardous · 1 d · 0.4%
How did Pima County's air break down in 2025?
Across 273 monitored days, 101 fell in the Good band (AQI 0–50) and 5 reached Unhealthy or worse. The worst single day peaked at AQI 357 (Hazardous).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 55 (Moderate).
Insights: Pima County, Arizona. EPA monitors recorded a median Air Quality Index of 55 across 273 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 101 (37%) fell in the Good band (AQI 0–50), 165 (60%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 84, while the worst single-day peak hit 357 (Hazardous). Residents averaged about 11.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM10 (127 days), Ozone (88 days), PM2.5 (58 days). Across the 2020–2025 trend window, good days shifted by -23 and the median AQI moved +0 points, placing the multi-year trajectory at improving. Residents and visitors experienced 5 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Apache (99.6% good, AQI 14); Cochise (65.6% good, AQI 46); Coconino (62.5% good, AQI 48); Gila (52.0% good, AQI 50); La Paz (68.6% good, AQI 47); Maricopa (16.4% good, AQI 71).
Air Quality Summary
Good Days
37.0%
101 of 273 monitored days
-38.0pp vs 75% target
Max AQI Recorded
357
Hazardous
Health Grade
Poor
90th-pct AQI 84
Pima County, Good days share 37.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Pima County, Unhealthy-or-worse share 1.8%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
101
37%
Moderate
165
60%
USG
2
1%
Unhealthy
3
1%
Very Unhealthy
1
0%
Hazardous
1
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Pima County.
- PM10 · 127 days · 46.5%
- Ozone · 88 days · 32.2%
- PM2.5 · 58 days · 21.2%
Health Impact Assessment
Poor
Pima County's air quality is rated Poor based on 37.0% good air days. There were 5 unhealthy days in 2025 when outdoor activity should be limited.
Air quality posed significant health risk in 2025. Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, pregnant women, and adults over 65, should monitor AirNow.gov alerts and limit outdoor activity on Unhealthy (AQI 151+) and Very Unhealthy (201+) days. Peak readings reached AQI 357, well into the Hazardous range.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is PM10, driving AQI on 127 of 273 monitored days.
5-Year Air Quality Trend
Air quality is improving in Pima County. Best year: 2022 (147 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 124 | 229 | 12 | 0 | 55 | 277 |
| 2021 | 93 | 258 | 13 | 0 | 56 | 313 |
| 2022 | 147 | 205 | 13 | 0 | 53 | 142 |
| 2023 | 123 | 235 | 7 | 0 | 54 | 147 |
| 2024 | 113 | 241 | 10 | 2 | 56 | 171 |
| 2025 | 101 | 165 | 2 | 3 | 55 | 357 |
How does Pima County compare?
How Pima County compares
Good-day share worse than US avg
Pima County 37.0%
Apache County, Arizona 99.6%
US average 76.5%
Median AQI worse than US avg
Pima County 55
Apache County, Arizona 14
US average 38
Unhealthy days / yr worse than US avg
Pima County 5
Apache County, Arizona 0
US average 0
Other Counties in Arizona
Air quality comparison for nearby counties in Arizona.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Pima County.
Butler County, Ohio
AQI 55 · 33.3% good
Cameron County, Texas
AQI 55 · 31.7% good
Montgomery County, Texas
AQI 55 · 30.7% good
Nueces County, Texas
AQI 55 · 35.0% good
Denver County, Colorado
AQI 54 · 44.2% good
Franklin County, Ohio
AQI 54 · 39.8% good
What Pima County's air means for you
On most days the air here is fine, but PM10 drives 5 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM10 days, the guide explains what a median of 55 means for exposure. Health guidance
- See how Pima County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Pima County with its Arizona neighbours before drawing a conclusion about the region. All of Arizona
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Pima County, Arizona? ▼
Pima County has a median Air Quality Index (AQI) of 55, rated "Moderate." 37.0% of monitored days (101 out of 273) had good air quality in 2025.
What is the main pollutant in Pima County? ▼
The primary pollutant in Pima County is Coarse Particles (PM10), which was the main AQI driver on 127 days (47% of monitored days). Irritates airways and can aggravate asthma and bronchitis.
How many unhealthy air days does Pima County have? ▼
In 2025, Pima County recorded 5 unhealthy air days (3 Unhealthy, 1 Very Unhealthy, 1 Hazardous). The maximum AQI reached 357.
Is the air quality in Pima County getting better or worse? ▼
Air quality in Pima County is improving based on 5-year trends (2020-2025). Best year: 2022 with 147 good days. Worst year: 2021 with 93 good days.
What does AQI 55 mean for health? ▼
Pima County's median AQI of 55 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Pima County compare to other counties in Arizona? ▼
Pima County has 37.0% good air days. Nearby counties in Arizona: Apache (99.6% good), Cochise (65.6% good), Coconino (62.5% good), Gila (52.0% good), La Paz (68.6% good), Maricopa (16.4% good).
What is the 90th percentile AQI in Pima County? ▼
The 90th percentile AQI for Pima County is 84, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 357 (Hazardous).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.