Arizona · County air quality · 2025

Maricopa County, Arizona

Median AQI 73 (Moderate). 8.8% of monitored days rated Good, direct from EPA Air Quality System stations.

73
Median AQI
8.8%
Good-air days
6
Unhealthy days
0%
Cleaner than US counties

Maricopa County's 2025 annual median AQI is 73 (Moderate), with 8.8% Good days

According to the U.S. EPA Air Quality System, Maricopa County, Arizona posted a 2025 median AQI of 73 (Moderate) across 365 monitored days, with 8.8% rated Good and 6 unhealthy or worse. This is an annual comparison, not today's advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US
Maricopa County's 8.8% Good-day share places it cleaner than 0% of US counties in 2025.
Closest median-AQI peer
Los Angeles County (10.7% Good, median AQI 74) is the closest nationwide median-AQI peer to Maricopa County.
2020–2025 trend
Maricopa County's floor-qualifying Good-day share is improving from 2020 to 2025 (3.8% → 8.8%).
Median AQI
Median AQI: 73

According to the 2025 EPA AQS county release on PlainAirData, Maricopa County, Arizona ranks #948 of 951 by median AQI (73) and #951 by good-day share (8.8%). 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

2024 → 2025
  • Maricopa County's peak single-day AQI rose from 261 to 366 between the 2024 and 2025 EPA annual releases, a change of +105 points.
  • Maricopa County's Unhealthy-category days fell from 7 to 3 between the 2024 and 2025 EPA annual releases, a change of -4 days.
  • Maricopa County's median AQI fell from 77 to 73 between the 2024 and 2025 EPA annual releases, a change of -4 points.

Compared against 366 monitored days in 2024 and 365 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Data updated August 2026

Maricopa County AQI category distribution Stacked-segment bar showing the share of monitored days that fell in each EPA AQI category, Good, Moderate, USG, Unhealthy, Very Unhealthy, Hazardous, with median AQI marker. AQI category distribution 365 monitored days M Median AQI 73 0 50 100 150 200 300 500 Maricopa County
  • Good · 32 d · 8.8%
  • Moderate · 295 d · 80.8%
  • USG · 32 d · 8.8%
  • Unhealthy · 3 d · 0.8%
  • Very Unhealthy · 1 d · 0.3%
  • Hazardous · 2 d · 0.5%

How did Maricopa County's air break down in 2025?

Across 365 monitored days, 32 fell in the Good band (AQI 0–50) and 6 reached Unhealthy or worse. The worst single day peaked at AQI 366 (Hazardous).

EPA AQS →
Maricopa County, Good days share 8.8%
National avg

Share of monitored days at AQI 0-50 (Good band).

Maricopa County, Unhealthy-or-worse share 16.4%
National avg

Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).

Where Maricopa County sits nationally

COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Maricopa County's Good-day share is 8.8% - cleaner than 0% of that comparison set.

Maricopa County Good-day share vs. every US county

Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release

8.8% 0th percentile higher than 0% of 951 US counties

0.0%–5.0%: 0 US counties (0%). Below this entry. 5.0%–10.0%: 1 US counties (0%). This entry sits in this band. 10.0%–15.0%: 4 US counties (0%). Above this entry. 15.0%–20.0%: 4 US counties (0%). Above this entry. 20.0%–25.0%: 1 US counties (0%). Above this entry. 25.0%–30.0%: 5 US counties (1%). Above this entry. 30.0%–35.0%: 9 US counties (1%). Above this entry. 35.0%–40.0%: 4 US counties (0%). Above this entry. 40.0%–45.0%: 16 US counties (2%). Above this entry. 45.0%–50.0%: 16 US counties (2%). Above this entry. 50.0%–55.0%: 32 US counties (3%). Above this entry. 55.0%–60.0%: 50 US counties (5%). Above this entry. 60.0%–65.0%: 77 US counties (8%). Above this entry. 65.0%–70.0%: 93 US counties (10%). Above this entry. 70.0%–75.0%: 109 US counties (11%). Above this entry. 75.0%–80.0%: 114 US counties (12%). Above this entry. 80.0%–85.0%: 123 US counties (13%). Above this entry. 85.0%–90.0%: 99 US counties (10%). Above this entry. 90.0%–95.0%: 117 US counties (12%). Above this entry. 95.0%–100.0%: 70 US counties (7%). Above this entry. 100.0%–105.0%: 7 US counties (1%). Above this entry. This county 0.0% 100% every floor-qualified US county, bucketed by value

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 Maricopa County.

Maricopa County, Arizona criteria pollutant distribution Stratified-band visualization showing the share of monitored days each criteria pollutant (PM2.5, PM10, O3, NO2, CO) was the primary AQI driver. Ozone · 46.6% PM10 · 29.3% PM2.5 · 24.1% 0% 25% 50% 75% 100% Maricopa County, Arizona · 365 monitored days Criteria pollutant column
  • Ozone · 170 days · 46.6%
  • PM10 · 107 days · 29.3%
  • PM2.5 · 88 days · 24.1%

2024 daily-monitor rhythm in Maricopa County

Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Jul posted the highest typical readings (median AQI 108, peak 166); Mar was cleanest at median 52. Summer months (Jun–Aug) averaged median AQI 92 vs 71 in Dec–Feb. 8 days crossed Unhealthy (AQI >150) at least once that year.

0 20 40 60 80 100 120 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 69 55 52 71 90 87 108 80 80 76 75 89
Maricopa County median daily AQI by calendar month (2024, EPA daily county file)

Five-year seasonal record

EPA day-level county files · 2020–2024

1,827 daily readings show a recurring local pattern: Apr has the highest matched-month median AQI (131), while Nov is lowest (73). Each cell is that month’s median daily AQI, not a current-air forecast.

JanFebMarAprMayJunJulAugSepOctNovDec
2020 751501722108771129213811927479
2021 14362192214939010810021319777101
2022 14366617584958410867517177
2023 67535487901051058064706782
2024 6955527190871088080767589

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

Very Poor

Maricopa County's air quality is rated Very Poor based on 8.8% good air days. There were 6 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 366, 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 170 of 365 monitored days.

5-Year Air Quality Trend

Air quality is improving in Maricopa County. Highest Good-day share: 2023 (11.2%, 41 of 365 monitored days).

Year Good Moderate USG Unhealthy Median AQI
2020 11 154 60 66 112
2021 12 128 91 61 122
2022 27 242 73 17 75
2023 41 256 61 7 72
2024 33 260 65 7 77
2025 32 295 32 3 73

How does Maricopa County compare?

How Maricopa County compares

Good-day share worse than typical
Maricopa County 8.8%
Los Angeles County, California 10.7%
Typical US county 76.0%
Median AQI worse than typical
Maricopa County 73
Los Angeles County, California 74
Typical US county 39
Unhealthy days / yr worse than typical
Maricopa County 6
Los Angeles County, California 32
Typical US county 1

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 Maricopa County, Arizona · 2020–2025

Embed this widget

Copy this snippet to embed a live-linked card on your own site. Attribution to PlainAirData is baked into the widget.

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.