Daily Air Quality Index summaries from EPA monitors in Palo Alto, Iowa, 1997–2025.
72%
Good days in 2025
40
Median daily AQI, 2025
9
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 Palo Alto, Iowa on 364 days. 263 of those days (72%) were in the Good range, and the median daily AQI was 40. That median is lower than the typical monitored county in Iowa (median 43.5 across 14 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 215 days. Across the years with fuller monitoring, the share of Good days fell: an average of 81% in 1998–2000 versus 68% in 2023–2025.
Years with fewer than 120 monitored days (1997) 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)
215
59%
Ozone
149
41%
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
263
92
9
0
0
0
40
71
134
PM2.5
2024
363
268
95
0
0
0
0
42
59
96
PM2.5
2023
364
211
135
14
4
0
0
46
80
161
PM2.5
2022
365
271
94
0
0
0
0
42
55
79
PM2.5
2021
362
250
108
2
2
0
0
43
64
167
PM2.5
2020
366
273
93
0
0
0
0
40
57
87
PM2.5
2019
364
246
118
0
0
0
0
44
60
93
PM2.5
2018
365
188
175
2
0
0
0
49
66
115
PM2.5
2017
365
193
171
1
0
0
0
49
61
115
PM2.5
2016
366
238
126
1
1
0
0
42
58
155
PM2.5
2015
365
190
174
1
0
0
0
50
63
102
PM2.5
2014
356
188
168
0
0
0
0
50
64
95
PM2.5
2013
365
220
144
1
0
0
0
46
66
101
PM2.5
2012
357
198
156
3
0
0
0
48
67
119
PM2.5
2011
365
195
170
0
0
0
0
49
67
100
PM2.5
2010
306
183
121
2
0
0
0
46
64
105
PM2.5
2009
264
199
64
1
0
0
0
39
62
135
Ozone
2008
264
219
45
0
0
0
0
36
55
96
Ozone
2007
255
203
50
2
0
0
0
36
59
108
Ozone
2006
291
237
53
1
0
0
0
38
58
103
Ozone
2005
355
288
65
2
0
0
0
36
58
114
Ozone
2004
366
352
13
1
0
0
0
27
44
102
Ozone
2003
362
324
38
0
0
0
0
28
51
84
Ozone
2002
365
328
37
0
0
0
0
27
51
100
Ozone
2001
364
345
18
1
0
0
0
31
46
108
Ozone
2000
231
180
46
5
0
0
0
42
67
133
Ozone
1999
208
172
32
4
0
0
0
42
64
122
Ozone
1998
189
155
31
3
0
0
0
40
67
129
Ozone
1997
28
27
1
0
0
0
0
29
48
80
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 Iowa with a similar median AQI in 2025
