Daily Air Quality Index summaries from EPA monitors in Santa Cruz, Arizona, 1985–2025.
52%
Good days in 2025
49
Median daily AQI, 2025
3
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Santa Cruz, Arizona on 364 days. 190 of those days (52%) were in the Good range, and the median daily AQI was 49. That median is about the same as the typical monitored county in Arizona (median 47 across 13 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 289 days. Across the years with fuller monitoring, the share of Good days rose: an average of 45% in 2005–2007 versus 62% in 2023–2025.
Years with fewer than 120 monitored days (1999, 2000, 2001, 2002, 2003, 2004…) 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)
289
79%
Coarse particles (PM10)
75
21%
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
364
190
171
2
1
0
0
49
73
187
PM2.5
2024
361
213
139
8
0
0
1
43
72
494
PM2.5
2023
358
265
92
1
0
0
0
37
63
145
PM2.5
2022
357
220
136
1
0
0
0
43
69
138
PM2.5
2021
360
169
189
1
1
0
0
52
71
171
PM2.5
2020
360
208
147
4
1
0
0
44
71
170
PM2.5
2019
362
250
110
2
0
0
0
39
67
120
PM2.5
2018
365
252
111
1
1
0
0
39
63
194
PM2.5
2017
365
236
125
2
2
0
0
40
65
198
PM2.5
2016
363
193
169
0
0
1
0
48
65
209
PM2.5
2015
365
261
101
3
0
0
0
38
65
135
PM2.5
2014
365
249
112
2
1
1
0
38
72
223
PM2.5
2013
344
228
111
3
2
0
0
41
67
159
PM2.5
2012
337
222
114
1
0
0
0
42
64
107
PM10
2011
352
209
141
2
0
0
0
44
73
104
PM10
2010
165
91
68
6
0
0
0
47
84
119
PM10
2009
346
191
153
1
1
0
0
47
76
195
PM10
2008
356
162
179
15
0
0
0
53
81
140
PM10
2007
358
161
183
14
0
0
0
52
88
140
PM10
2006
333
136
154
39
4
0
0
55
108
184
PM10
2005
304
151
123
21
9
0
0
51
100
199
PM10
2004
62
23
39
0
0
0
0
54
65
93
PM2.5
2003
61
26
33
2
0
0
0
52
81
115
PM2.5
2002
61
18
42
1
0
0
0
54
76
117
PM2.5
2001
63
27
34
2
0
0
0
53
67
130
PM2.5
2000
60
21
37
2
0
0
0
55
84
106
PM2.5
1999
59
19
37
3
0
0
0
55
79
135
PM2.5
1998
50
37
11
2
0
0
0
33
68
108
PM10
1997
51
42
9
0
0
0
0
30
56
86
PM10
1996
42
30
12
0
0
0
0
29
65
80
PM10
1995
67
59
8
0
0
0
0
30
53
85
PM10
1994
84
72
12
0
0
0
0
29
53
81
PM10
1993
45
30
15
0
0
0
0
35
59
83
PM10
1992
53
30
23
0
0
0
0
44
69
100
PM10
1991
58
35
22
1
0
0
0
43
68
105
PM10
1990
52
32
19
1
0
0
0
38
71
111
PM10
1989
42
22
18
2
0
0
0
49
71
145
PM10
1988
45
19
25
1
0
0
0
54
89
101
PM10
1987
47
23
21
3
0
0
0
51
87
139
PM10
1986
41
14
25
2
0
0
0
57
85
128
PM10
1985
19
11
8
0
0
0
0
49
67
78
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 Arizona with a similar median AQI in 2025
