Daily Air Quality Index summaries from EPA monitors in San Diego, California, 1980–2025.
18%
Good days in 2025
67
Median daily AQI, 2025
33
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 San Diego, California on 365 days. 64 of those days (18%) were in the Good range, and the median daily AQI was 67. 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 180 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 16% in 1980–1982 versus 16% 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)
180
49%
Ozone
176
48%
Coarse particles (PM10)
9
2%
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
64
268
26
7
0
0
67
100
161
PM2.5
2024
366
47
267
48
4
0
0
71
105
161
Ozone
2023
365
61
260
44
0
0
0
67
101
150
Ozone
2022
365
42
297
25
1
0
0
63
97
156
PM2.5
2021
365
52
297
16
0
0
0
67
90
133
PM2.5
2020
366
33
284
35
14
0
0
74
108
192
PM2.5
2019
365
38
302
23
2
0
0
66
93
169
PM2.5
2018
365
28
302
35
0
0
0
67
100
143
PM2.5
2017
365
41
262
56
6
0
0
68
112
174
Ozone
2016
366
30
294
40
2
0
0
68
105
164
PM2.5
2015
365
46
278
40
1
0
0
65
102
156
PM2.5
2014
365
48
278
37
2
0
0
65
101
170
PM2.5
2013
365
23
305
35
1
0
1
67
101
630
PM2.5
2012
366
26
304
35
1
0
0
67
100
170
PM2.5
2011
365
21
310
30
4
0
0
66
100
169
PM2.5
2010
365
35
305
21
4
0
0
64
93
192
PM2.5
2009
365
33
283
44
5
0
0
69
108
179
PM2.5
2008
366
32
260
63
10
1
0
74
117
204
Ozone
2007
365
51
253
51
8
2
0
67
115
257
Ozone
2006
365
57
237
55
16
0
0
71
126
187
Ozone
2005
365
59
251
50
5
0
0
69
111
159
Ozone
2004
366
44
267
49
6
0
0
70
112
174
PM2.5
2003
365
47
239
71
7
0
1
71
126
328
PM2.5
2002
365
28
262
64
11
0
0
76
117
187
PM2.5
2001
365
13
261
76
14
1
0
77
129
212
PM2.5
2000
366
50
219
81
15
1
0
76
133
201
Ozone
1999
365
15
248
85
17
0
0
82
129
187
Ozone
1998
365
131
146
54
26
8
0
61
147
238
Ozone
1997
365
114
179
58
13
1
0
65
126
207
Ozone
1996
366
117
156
64
27
2
0
68
143
213
Ozone
1995
365
108
127
88
35
7
0
77
154
218
Ozone
1994
365
85
149
88
39
4
0
79
159
217
Ozone
1993
365
98
138
74
44
11
0
80
159
252
Ozone
1992
366
83
134
86
57
6
0
89
174
229
Ozone
1991
365
66
143
94
45
17
0
89
177
242
Ozone
1990
365
55
119
100
64
27
0
103
190
242
Ozone
1989
365
31
110
106
81
37
0
110
201
293
Ozone
1988
366
34
108
112
71
41
0
114
202
254
Ozone
1987
365
52
131
91
62
29
0
100
190
296
Ozone
1986
365
54
123
109
59
20
0
101
182
240
Ozone
1985
365
58
117
85
70
35
0
103
200
266
Ozone
1984
366
45
135
92
55
39
0
101
202
255
Ozone
1983
365
87
116
69
55
38
0
90
201
256
Ozone
1982
365
75
127
82
48
33
0
90
200
260
Ozone
1981
365
43
104
93
75
50
0
116
203
274
Ozone
1980
366
62
95
74
60
75
0
110
222
272
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
