Arizona · County air quality · 2025
Pima County, Arizona
Median AQI 54 (Moderate). 33.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 54
- Median AQI
- 33.7%
- Good-air days
- 5
- Unhealthy days
- 2%
- Cleaner than US counties
Pima County's 2025 annual median AQI is 54 (Moderate), with 33.7% Good days
According to the U.S. EPA Air Quality System, Pima County, Arizona posted a 2025 median AQI of 54 (Moderate) across 365 monitored days, with 33.7% rated Good and 5 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Pima County's 33.7% Good-day share places it cleaner than 2% of US counties in 2025.
- Closest median-AQI peer
- Hamilton County (34.3% Good, median AQI 54) is the closest nationwide median-AQI peer to Pima County.
- 2020–2025 trend
- Pima County's floor-qualifying Good-day share is stable from 2020 to 2025 (34.0% → 33.9%).
- Median AQI
- Median AQI: 54
According to the 2025 EPA AQS county release on PlainAirData, Pima County, Arizona ranks #925 of 951 by median AQI (54) and #931 by good-day share (33.7%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Pima County's peak single-day AQI rose from 171 to 357 between the 2024 and 2025 EPA annual releases, a change of +186 points.
- Pima County's Good-day share rose from 30.9% to 33.7% between the 2024 and 2025 EPA annual releases, a change of +2.8 percentage points.
- Pima County's Unhealthy-category days rose from 2 to 3 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Data updated August 2026
- Good · 123 d · 33.7%
- Moderate · 234 d · 64.1%
- USG · 3 d · 0.8%
- Unhealthy · 3 d · 0.8%
- Very Unhealthy · 1 d · 0.3%
- Hazardous · 1 d · 0.3%
How did Pima County's air break down in 2025?
Across 365 monitored days, 123 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 →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Pima County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Pima County's Good-day share is 33.7% - cleaner than 2% of that comparison set.
Pima County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
33.7% 2nd percentile higher than 2% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Pima County.
- Ozone · 186 days · 51.0%
- PM2.5 · 112 days · 30.7%
- PM10 · 67 days · 18.4%
2024 daily-monitor rhythm in Pima County
Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). May posted the highest typical readings (median AQI 77, peak 105); Feb was cleanest at median 44. Summer months (Jun–Aug) averaged median AQI 66 vs 49 in Dec–Feb. 2 days crossed Unhealthy (AQI >150) at least once that year.
Five-year seasonal record
EPA day-level county files · 2020–20241,827 daily readings show a recurring local pattern: Jul has the highest matched-month median AQI (69), while Feb is lowest (48). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Pima County's air quality is rated Poor based on 33.7% 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 Ozone, driving AQI on 186 of 365 monitored days.
5-Year Air Quality Trend
Air quality is stable in Pima County. Highest Good-day share: 2022 (40.3%, 147 of 365 monitored 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 | 123 | 234 | 3 | 3 | 54 | 357 |
How does Pima County compare?
How Pima County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Pima County, Arizona · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.