Daily Air Quality Index summaries from EPA monitors in Kittitas, Washington, 1993–2025.
80%
Good days in 2025
25
Median daily AQI, 2025
3
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 Kittitas, Washington on 365 days. 292 of those days (80%) were in the Good range, and the median daily AQI was 25. That median is lower than the typical monitored county in Washington (median 28 across 30 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 365 days. Across the years with fuller monitoring, the share of Good days fell: an average of 93% in 1996–1998 versus 82% in 2023–2025.
Years with fewer than 120 monitored days (1993, 1994, 1995, 1999, 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
Fine particles (PM2.5)
365
100%
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
292
70
3
0
0
0
25
57
114
PM2.5
2024
366
320
46
0
0
0
0
23
53
94
PM2.5
2023
365
287
74
1
1
2
0
29
58
254
PM2.5
2022
364
259
100
3
2
0
0
28
74
164
PM2.5
2021
365
303
57
3
2
0
0
28
55
173
PM2.5
2020
365
297
57
2
3
2
4
24
59
724
PM2.5
2019
365
268
97
0
0
0
0
31
61
96
PM2.5
2018
358
290
56
5
6
1
0
26
62
221
PM2.5
2017
355
235
104
11
3
2
0
38
75
240
PM2.5
2016
366
288
72
6
0
0
0
25
63
143
PM2.5
2015
363
281
78
2
2
0
0
28
64
159
PM2.5
2014
323
272
50
0
1
0
0
21
57
170
PM2.5
2013
348
266
82
0
0
0
0
23
62
94
PM2.5
2012
361
260
84
11
5
0
1
28
70
307
PM2.5
2011
354
279
68
6
1
0
0
23
62
153
PM2.5
2010
365
270
95
0
0
0
0
26
65
99
PM2.5
2009
363
268
95
0
0
0
0
33
60
85
PM2.5
2008
362
266
94
2
0
0
0
28
64
119
PM2.5
2007
347
261
86
0
0
0
0
36
58
89
PM2.5
2006
360
238
122
0
0
0
0
42
61
90
PM2.5
2005
355
259
96
0
0
0
0
38
61
92
PM2.5
2004
141
129
12
0
0
0
0
17
47
55
PM2.5
2003
119
114
5
0
0
0
0
14
41
56
PM2.5
2002
124
119
5
0
0
0
0
18
37
65
PM2.5
2001
126
122
4
0
0
0
0
19
37
58
PM10
2000
124
117
7
0
0
0
0
19
45
81
PM2.5
1999
114
113
1
0
0
0
0
17
33
54
PM10
1998
152
143
9
0
0
0
0
22
41
79
PM2.5
1997
165
152
13
0
0
0
0
21
47
79
PM10
1996
140
131
9
0
0
0
0
19
44
78
PM2.5
1995
102
97
5
0
0
0
0
16
36
57
PM2.5
1994
97
92
5
0
0
0
0
17
42
61
PM2.5
1993
48
42
6
0
0
0
0
28
54
60
PM2.5
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 Washington with a similar median AQI in 2025
