Daily Air Quality Index summaries from EPA monitors in Chelan, Washington, 1986–2025.
70%
Good days in 2025
35
Median daily AQI, 2025
14
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 Chelan, Washington on 365 days. 254 of those days (70%) were in the Good range, and the median daily AQI was 35. That median is higher 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 rose: an average of 57% in 2004–2006 versus 75% in 2023–2025.
Years with fewer than 120 monitored days (1998, 1999, 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
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
254
97
5
8
1
0
35
68
233
PM2.5
2024
366
293
68
4
1
0
0
28
62
158
PM2.5
2023
365
280
80
1
2
2
0
34
59
266
PM2.5
2022
365
246
96
8
13
2
0
34
74
290
PM2.5
2021
365
279
81
2
3
0
0
31
58
195
PM2.5
2020
366
274
80
1
6
1
4
28
59
817
PM2.5
2019
365
258
106
1
0
0
0
32
61
102
PM2.5
2018
365
244
96
8
10
5
2
36
72
627
PM2.5
2017
365
236
108
9
8
4
0
37
72
293
PM2.5
2016
366
284
82
0
0
0
0
29
56
81
PM2.5
2015
362
243
116
3
0
0
0
33
65
148
PM2.5
2014
362
234
120
6
2
0
0
33
68
154
PM2.5
2013
365
230
135
0
0
0
0
36
69
99
PM2.5
2012
366
213
128
10
13
1
1
42
78
443
PM2.5
2011
363
233
123
6
1
0
0
33
74
153
PM2.5
2010
365
251
112
2
0
0
0
29
67
121
PM2.5
2009
365
230
135
0
0
0
0
36
67
93
PM2.5
2008
366
206
159
1
0
0
0
43
74
112
PM2.5
2007
365
224
141
0
0
0
0
42
71
96
PM2.5
2006
365
198
165
2
0
0
0
48
66
104
PM2.5
2005
349
221
126
2
0
0
0
40
68
115
PM2.5
2004
122
67
55
0
0
0
0
48
75
87
PM2.5
2003
41
41
0
0
0
0
0
14
28
42
PM10
2002
76
76
0
0
0
0
0
17
34
47
PM10
2001
90
87
3
0
0
0
0
19
36
79
PM10
2000
85
85
0
0
0
0
0
19
36
47
PM10
1999
45
45
0
0
0
0
0
15
23
44
PM10
1998
54
54
0
0
0
0
0
20
38
43
PM10
1997
73
69
4
0
0
0
0
20
40
60
PM10
1996
85
82
3
0
0
0
0
19
36
66
PM10
1995
78
73
5
0
0
0
0
19
45
58
PM10
1994
70
67
1
1
0
1
0
19
38
210
PM10
1993
48
47
1
0
0
0
0
21
41
54
PM10
1992
44
44
0
0
0
0
0
18
31
38
PM10
1991
48
47
1
0
0
0
0
18
36
60
PM10
1990
49
48
1
0
0
0
0
17
31
52
PM10
1989
48
48
0
0
0
0
0
19
34
39
PM10
1988
42
42
0
0
0
0
0
20
37
50
PM10
1987
33
28
5
0
0
0
0
30
54
59
PM10
1986
36
32
4
0
0
0
0
30
51
57
PM10
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
