Daily Air Quality Index summaries from EPA monitors in Imperial, California, 1980–2025.
28%
Good days in 2025
64
Median daily AQI, 2025
44
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 Imperial, California on 365 days. 101 of those days (28%) were in the Good range, and the median daily AQI was 64. 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 ozone on 192 days. Across the years with fuller monitoring, the share of Good days fell: an average of 66% in 1980–1982 versus 26% in 2023–2025.
Years with fewer than 120 monitored days (1984) 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
192
53%
Coarse particles (PM10)
100
27%
Fine particles (PM2.5)
72
20%
Nitrogen dioxide (NO₂)
1
<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
101
220
34
9
0
1
64
108
426
Ozone
2024
366
83
233
42
5
2
1
63
107
341
Ozone
2023
365
104
214
37
3
3
4
61
105
506
Ozone
2022
365
86
232
34
5
2
6
61
106
791
PM2.5
2021
365
84
252
22
4
1
2
60
97
436
Ozone
2020
366
94
244
26
2
0
0
60
97
166
Ozone
2019
365
94
250
19
2
0
0
61
93
185
Ozone
2018
365
67
248
41
7
2
0
64
108
286
PM2.5
2017
365
73
250
37
2
2
1
64
104
328
PM2.5
2016
366
64
257
39
3
1
2
61
105
546
PM2.5
2015
365
49
274
39
3
0
0
66
105
184
PM2.5
2014
365
24
287
45
5
2
2
69
112
352
PM2.5
2013
365
137
189
35
3
1
0
58
101
207
Ozone
2012
366
160
167
34
4
1
0
55
101
274
Ozone
2011
365
176
156
32
1
0
0
52
93
168
Ozone
2010
365
151
163
51
0
0
0
57
108
140
Ozone
2009
365
142
171
50
2
0
0
58
105
161
Ozone
2008
366
160
173
28
5
0
0
54
97
169
Ozone
2007
365
128
182
46
9
0
0
58
112
190
Ozone
2006
365
106
196
54
9
0
0
63
119
190
Ozone
2005
365
113
183
59
10
0
0
61
119
187
Ozone
2004
366
115
205
44
2
0
0
61
105
164
Ozone
2003
365
122
179
54
9
0
1
62
113
762
Ozone
2002
365
86
212
53
13
1
0
67
122
227
Ozone
2001
365
98
196
52
15
3
1
66
126
548
Ozone
2000
366
128
185
41
10
2
0
61
115
208
Ozone
1999
365
63
194
86
20
2
0
77
140
217
Ozone
1998
365
80
186
79
19
1
0
76
136
216
Ozone
1997
365
78
135
102
41
8
1
87
163
420
Ozone
1996
366
99
161
70
30
6
0
74
150
245
Ozone
1995
365
99
147
67
40
12
0
76
164
250
Ozone
1994
365
78
147
95
44
1
0
87
154
212
Ozone
1993
365
126
145
74
17
3
0
62
140
224
Ozone
1992
364
174
111
56
20
3
0
54
132
213
Ozone
1991
338
225
90
19
3
1
0
42
84
232
Ozone
1990
364
298
60
5
1
0
0
38
61
152
Ozone
1989
345
268
65
8
3
0
1
38
74
580
Ozone
1988
323
209
87
23
3
1
0
44
93
220
Ozone
1987
348
272
72
4
0
0
0
37
67
136
Ozone
1986
245
198
43
4
0
0
0
37
71
133
Ozone
1985
228
126
66
28
8
0
0
46
115
192
Ozone
1984
23
23
0
0
0
0
0
23
28
29
Ozone
1983
335
271
53
11
0
0
0
34
67
133
Ozone
1982
328
275
46
7
0
0
0
37
61
136
Ozone
1981
316
187
96
28
4
1
0
46
101
205
Ozone
1980
356
194
95
40
23
4
0
48
140
208
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
