Daily Air Quality Index summaries from EPA monitors in Montgomery, Texas, 1988–2025.
39%
Good days in 2025
53
Median daily AQI, 2025
8
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Montgomery, Texas on 363 days. 142 of those days (39%) were in the Good range, and the median daily AQI was 53. That median is higher than the typical monitored county in Texas (median 43.5 across 44 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 242 days. Across the years with fuller monitoring, the share of Good days fell: an average of 63% in 1988–2001 versus 37% in 2023–2025.
Years with fewer than 120 monitored days (1999) 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)
242
67%
Ozone
121
33%
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
363
142
213
8
0
0
0
53
67
133
PM2.5
2024
363
111
231
20
1
0
0
55
86
166
PM2.5
2023
364
151
204
9
0
0
0
53
75
122
PM2.5
2022
364
175
183
6
0
0
0
51
71
126
PM2.5
2021
359
204
152
2
1
0
0
47
66
151
PM2.5
2020
366
219
139
8
0
0
0
44
64
129
PM2.5
2019
365
261
99
5
0
0
0
44
61
143
Ozone
2018
365
231
123
10
1
0
0
44
74
156
PM2.5
2017
363
227
129
7
0
0
0
46
68
140
PM2.5
2016
366
197
165
4
0
0
0
49
63
133
PM2.5
2015
365
195
165
5
0
0
0
48
74
133
PM2.5
2014
365
186
175
4
0
0
0
49
67
133
PM2.5
2013
363
194
163
6
0
0
0
48
69
150
PM2.5
2012
365
189
164
12
0
0
0
49
66
150
PM2.5
2011
362
180
167
14
1
0
0
51
77
164
Ozone
2010
360
153
201
6
0
0
0
53
71
143
PM2.5
2009
365
162
203
0
0
0
0
53
68
90
PM2.5
2008
361
170
183
8
0
0
0
52
74
150
PM2.5
2007
364
163
188
13
0
0
0
52
72
126
PM2.5
2006
365
140
204
15
5
1
0
54
90
205
PM2.5
2005
354
104
226
22
1
1
0
55
87
219
PM2.5
2004
365
241
114
9
1
0
0
42
70
197
Ozone
2003
362
238
109
9
4
2
0
44
74
213
Ozone
2002
362
238
107
14
2
1
0
42
80
203
Ozone
2001
322
213
85
18
6
0
0
44
87
195
Ozone
2000
366
219
99
32
15
1
0
44
122
201
Ozone
1999
86
54
24
5
2
1
0
44
100
201
Ozone
1988
282
181
55
25
17
4
0
43
140
210
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 Texas with a similar median AQI in 2025
