Arizona Air Quality

EPA monitor data through 2025 · Updated August 13, 2026 · Methods

In 2025, Arizona recorded 69 days above an Air Quality Index of 100, the level at which EPA begins warning sensitive groups, out of 365 days with monitoring data. Most of those bad days were driven by ozone. Under the AQI rules that applied before 2013, the same air would have scored 46 days. Since 2000, unhealthy days are 68% lower on a consistent definition.

Unhealthy days, 2025

AQI above 100

Same air, pre-2013 rules

for comparison with older reports

Good-air days

AQI 50 or below

Days monitored

365

full year

How to read a statewide figure. The Air Quality Index describes one place at one time. A statewide number is the worst monitor anywhere in the state on each day, so it answers “was the air unhealthy somewhere in Arizona?” — not “what did a typical resident breathe?” In a large state with many monitors it will read high even if most of the state was clean. EPA publishes the AQI for metropolitan areas rather than states for exactly this reason. For what people actually breathed, use the metro pages below.

Unhealthy days by year, scored two ways

EPA changed what an AQI of 100 means in 2013 and again in 2015, so a count published before those changes is not comparable to one published after. Each panel below applies a single fixed rulebook to every year, so each is internally consistent. Why this matters.

Scored by today's rules

Scored by the pre-2013 rules

What 2025 looked like

Air quality category	Days	Share of monitored days
Good	11	3%
Moderate	285	78%
Unhealthy for sensitive groups	53	15%
Unhealthy or worse	16	4%

Median AQI 80 · 90th-percentile AQI 114 · worst day 1215. Scored under current rules.

What drove the unhealthy days

Of the 69 days above 100 in 2025, 26 were driven by ozone and 6 by fine particles, with 37 from another pollutant. The two behave differently. Ozone peaks on hot sunny afternoons; fine particles now spike mainly with wildfire smoke. In the western United States, ozone is a different problem: the floor is rising, with even the cleanest summer days at high elevation now near 40 ppb, and bad years track wildfire seasons. Domestic emission cuts have less room to work against that.

The unhealthy days in 2025

Every day the index passed 100, what it reached, and which pollutant drove it. 23 of these 69 would not have counted as unhealthy under the pre-2013 rules.

Date	Peak AQI	Driven by	Pre-2013 score
Jan 1	366	Fine particles	309
Jan 2	117	Fine particles	110
Jan 7	147	Coarse particles	147
Jan 8	1215	Coarse particles	1143
Jan 20	127	Coarse particles	127
Jan 22	107	Coarse particles	107
Feb 6	113	Fine particles	100 (not unhealthy)
Feb 7	102	Coarse particles	102
Feb 11	109	Coarse particles	109
Feb 25	109	Coarse particles	109
Feb 27	171	Coarse particles	171
Mar 1	579	Coarse particles	571
Mar 2	121	Coarse particles	121
Mar 3	123	Coarse particles	123
Mar 13	378	Coarse particles	387
Apr 1	144	Coarse particles	144
Apr 8	105	Ozone	90 (not unhealthy)
Apr 9	108	Ozone	100 (not unhealthy)
Apr 10	108	Ozone	93 (not unhealthy)
Apr 11	112	Ozone	97 (not unhealthy)
Apr 18	763	Coarse particles	737
Apr 21	101	Ozone	87 (not unhealthy)
Apr 25	131	Coarse particles	131
May 1	108	Ozone	93 (not unhealthy)
May 4	103	Coarse particles	103
May 10	126	Coarse particles	126
May 11	101	Ozone	87 (not unhealthy)
May 15	101	Ozone	87 (not unhealthy)
May 20	101	Ozone	87 (not unhealthy)
May 21	119	Ozone	107
May 22	101	Ozone	87 (not unhealthy)
May 25	105	Ozone	90 (not unhealthy)
May 26	101	Ozone	87 (not unhealthy)
May 27	122	Ozone	104
May 28	122	Ozone	104
May 29	105	Coarse particles	105
May 30	101	Ozone	98 (not unhealthy)
Jun 6	108	Ozone	93 (not unhealthy)
Jun 7	122	Ozone	104
Jun 9	101	Ozone	87 (not unhealthy)
Jun 12	110	Coarse particles	110
Jun 14	109	Coarse particles	109
Jun 18	112	Ozone	97 (not unhealthy)
Jun 19	115	Coarse particles	115
Jun 28	115	Coarse particles	115
Jun 30	189	Coarse particles	189
Jul 1	357	Coarse particles	364
Jul 20	131	Coarse particles	131
Aug 10	151	Coarse particles	151
Aug 13	101	Coarse particles	101
Aug 20	143	Ozone	119
Aug 21	559	Coarse particles	553
Aug 22	253	Coarse particles	253
Aug 23	101	Ozone	87 (not unhealthy)
Aug 24	105	Ozone	90 (not unhealthy)
Aug 25	647	Coarse particles	632
Aug 26	119	Ozone	101
Aug 27	101	Ozone	87 (not unhealthy)
Aug 28	112	Ozone	97 (not unhealthy)
Aug 31	162	Coarse particles	162
Sep 1	129	Coarse particles	129
Sep 2	331	Coarse particles	335
Sep 3	329	Coarse particles	332
Sep 17	117	Coarse particles	117
Sep 26	308	Coarse particles	309
Oct 8	123	Coarse particles	123
Nov 28	139	Fine particles	122
Dec 7	102	Fine particles	91 (not unhealthy)
Dec 25	104	Fine particles	93 (not unhealthy)

Metro areas in Arizona

Ranked by unhealthy days in their latest year. These are the geographies EPA actually reports the AQI for.

Metro area	Unhealthy days	Pre-2013 rules	Main driver
Phoenix-Mesa-Scottsdale, AZ	56	39	ozone
Payson, AZ	15	7	ozone
Tucson, AZ	8	7	ozone and fine particles equally
Yuma, AZ	7	6	ozone
Sierra Vista-Douglas, AZ	4	4	ozone and fine particles equally
Nogales, AZ	3	2	fine particles
Flagstaff, AZ	2	0	ozone and fine particles equally
Lake Havasu City-Kingman, AZ	2	2	ozone and fine particles equally
Prescott, AZ	0	0	ozone and fine particles equally
Show Low, AZ	0	0	ozone and fine particles equally

The full series

Year	Unhealthy days, current rules	Pre-2013 rules	Days monitored
2000	174	142	366
2001	90	57	365
2002	101	57	365
2003	98	64	365
2004	69	30	366
2005	120	91	365
2006	273	265	365
2007	232	214	365
2008	210	198	366
2009	84	71	365
2010	73	51	365
2011	144	123	365
2012	119	97	366
2013	112	93	365
2014	129	112	365
2015	82	53	365
2016	85	60	366
2017	103	77	365
2018	91	67	365
2019	63	38	365
2020	236	215	366
2021	243	207	365
2022	121	93	365
2023	98	74	365
2024	130	89	366
2025	69	46	365

Sources

EPA AirData daily monitor files, recomputed under both breakpoint tables. Methods and validation.
Download the full dataset for every state and metro.