Daily Air Quality Index summaries from EPA monitors in Orange, California, 1980–2025.
38%
Good days in 2025
53
Median daily AQI, 2025
13
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 Orange, California on 365 days. 138 of those days (38%) were in the Good range, and the median daily AQI was 53. That median is higher than the typical monitored county in California (median 45.5 across 46 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 236 days. Across the years with fuller monitoring, the share of Good days rose: an average of 17% in 1980–1982 versus 38% in 2023–2025.
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)
236
65%
Ozone
119
33%
Nitrogen dioxide (NO₂)
8
2%
Coarse particles (PM10)
2
1%
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
138
214
11
2
0
0
53
79
159
PM2.5
2024
366
119
231
13
3
0
0
54
84
172
PM2.5
2023
365
160
195
9
1
0
0
52
77
166
PM2.5
2022
365
143
215
5
2
0
0
53
71
156
PM2.5
2021
365
109
238
18
0
0
0
55
87
148
PM2.5
2020
366
118
207
28
11
2
0
56
108
218
PM2.5
2019
365
157
192
15
1
0
0
53
87
172
Ozone
2018
365
114
233
15
3
0
0
54
86
160
PM2.5
2017
365
86
247
30
2
0
0
59
97
151
PM2.5
2016
366
87
264
13
2
0
0
58
88
169
PM2.5
2015
365
57
287
19
2
0
0
61
87
156
PM2.5
2014
365
35
309
19
2
0
0
63
87
156
PM2.5
2013
365
79
274
12
0
0
0
59
75
143
PM2.5
2012
366
75
279
12
0
0
0
60
84
147
PM2.5
2011
365
43
308
14
0
0
0
62
88
143
PM2.5
2010
365
65
292
7
1
0
0
61
82
177
PM2.5
2009
365
78
262
21
4
0
0
61
93
174
PM2.5
2008
366
74
250
36
6
0
0
67
101
197
PM2.5
2007
365
75
261
23
4
1
1
58
93
372
PM2.5
2006
365
84
250
21
9
1
0
60
97
209
PM2.5
2005
365
81
256
27
1
0
0
61
94
157
PM2.5
2004
366
49
241
66
10
0
0
70
126
179
Ozone
2003
365
58
246
48
13
0
0
66
116
200
PM2.5
2002
365
56
264
42
3
0
0
67
105
169
PM2.5
2001
365
80
224
50
11
0
0
66
115
179
PM2.5
2000
366
69
241
36
19
1
0
65
127
205
PM2.5
1999
365
109
204
47
5
0
0
64
105
164
NO2
1998
365
186
138
36
4
1
0
50
101
210
NO2
1997
365
175
161
26
3
0
0
51
97
187
NO2
1996
366
165
145
48
8
0
0
53
105
195
NO2
1995
365
128
165
65
6
1
0
61
109
204
NO2
1994
365
106
175
69
8
7
0
66
113
271
NO2
1993
365
127
151
67
15
5
0
67
126
218
NO2
1992
366
105
166
62
23
10
0
68
140
256
NO2
1991
365
95
155
79
27
9
0
74
143
242
NO2
1990
365
81
151
98
20
15
0
79
150
239
NO2
1989
365
63
164
97
24
17
0
87
157
265
NO2
1988
366
68
157
97
25
19
0
89
156
295
NO2
1987
365
65
180
69
34
17
0
79
169
263
NO2
1986
365
75
142
90
24
34
0
89
192
256
NO2
1985
365
75
149
73
25
43
0
79
208
289
NO2
1984
366
54
157
83
42
30
0
89
192
276
NO2
1983
365
77
139
77
27
45
0
87
207
296
NO2
1982
365
63
159
95
19
29
0
79
177
268
NO2
1981
365
55
136
109
28
37
0
100
201
289
NO2
1980
366
63
130
86
40
47
0
100
214
277
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 California with a similar median AQI in 2025
