Daily Air Quality Index summaries from EPA monitors in Washington, Utah, 1995–2025.
75%
Good days in 2025
44
Median daily AQI, 2025
0
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Washington, Utah on 365 days. 274 of those days (75%) were in the Good range, and the median daily AQI was 44. That median is about the same as the typical monitored county in Utah (median 45 across 15 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 333 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 75% in 1995–1997 versus 77% in 2023–2025.
Years with fewer than 120 monitored days (1998, 2000, 2001, 2002, 2003) are shown in the table but left out of comparisons and trend statements.
How the days broke down each year
Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Typical and high-end AQI over time
The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.
Median daily AQI
90th-percentile daily AQI
Main pollutant by day, 2025
On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.
Pollutant
Days as main pollutant
Share of monitored days
Ozone
333
91%
Fine particles (PM2.5)
32
9%
Year-by-year data
Annual AQI summary by year
Year
Days with AQI
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Median AQI
90th pct.
Max AQI
Main pollutant
2025
365
274
91
0
0
0
0
44
64
97
Ozone
2024
366
278
86
2
0
0
0
44
67
108
Ozone
2023
365
291
74
0
0
0
0
43
61
90
Ozone
2022
365
288
77
0
0
0
0
44
61
97
Ozone
2021
365
256
106
2
1
0
0
45
64
163
Ozone
2020
366
276
87
3
0
0
0
44
63
112
Ozone
2019
365
283
82
0
0
0
0
45
61
93
Ozone
2018
365
223
141
1
0
0
0
44
74
108
Ozone
2017
365
256
108
1
0
0
0
45
71
101
Ozone
2016
366
281
85
0
0
0
0
43
63
87
Ozone
2015
365
276
86
3
0
0
0
43
67
108
Ozone
2014
365
284
80
1
0
0
0
44
61
101
Ozone
2013
365
274
89
2
0
0
0
44
67
112
Ozone
2012
366
228
126
12
0
0
0
47
80
133
Ozone
2011
363
235
123
5
0
0
0
46
77
108
Ozone
2010
365
210
147
8
0
0
0
48
80
108
Ozone
2009
354
239
112
3
0
0
0
46
67
126
Ozone
2008
360
218
135
7
0
0
0
48
80
119
Ozone
2007
326
199
123
4
0
0
0
46
77
122
Ozone
2006
359
229
123
7
0
0
0
46
84
119
Ozone
2005
355
233
101
17
3
1
0
46
84
204
Ozone
2004
340
216
112
12
0
0
0
47
87
133
Ozone
2003
116
114
2
0
0
0
0
17
33
63
PM2.5
2002
103
102
1
0
0
0
0
17
32
62
PM2.5
2001
113
111
2
0
0
0
0
17
29
53
PM2.5
2000
83
82
1
0
0
0
0
18
32
53
PM2.5
1998
29
20
8
1
0
0
0
33
62
137
PM2.5
1997
269
220
41
8
0
0
0
32
71
122
Ozone
1996
326
222
91
13
0
0
0
32
84
143
Ozone
1995
145
108
37
0
0
0
0
43
64
90
Ozone
What this data can and can’t tell you
It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.
It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.
Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.
Counties in Utah with a similar median AQI in 2025
