Daily Air Quality Index summaries from EPA monitors in Ravalli, Montana, 1986–2025.
79%
Good days in 2025
21
Median daily AQI, 2025
1
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Ravalli, Montana on 361 days. 286 of those days (79%) were in the Good range, and the median daily AQI was 21. That median is lower than the typical monitored county in Montana (median 25.5 across 18 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 361 days. Across the years with fuller monitoring, the share of Good days fell: an average of 95% in 1994–1996 versus 77% in 2023–2025.
Years with fewer than 120 monitored days (1986, 1987) 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)
361
100%
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
361
286
74
1
0
0
0
21
59
123
PM2.5
2024
362
254
92
10
6
0
0
24
73
182
PM2.5
2023
363
293
69
1
0
0
0
22
58
110
PM2.5
2022
363
287
64
2
8
2
0
27
64
263
PM2.5
2021
358
268
67
18
5
0
0
28
76
159
PM2.5
2020
361
301
52
3
5
0
0
15
59
185
PM2.5
2019
364
303
61
0
0
0
0
19
55
77
PM2.5
2018
351
280
71
0
0
0
0
24
62
90
PM2.5
2017
360
209
111
25
15
0
0
42
107
198
PM2.5
2016
351
245
95
9
2
0
0
34
67
160
PM2.5
2015
351
268
62
8
9
4
0
28
71
272
PM2.5
2014
354
260
92
2
0
0
0
31
64
117
PM2.5
2013
346
230
109
7
0
0
0
36
70
124
PM2.5
2012
354
229
84
11
24
5
1
36
118
322
PM2.5
2011
363
278
78
6
1
0
0
28
65
154
PM2.5
2010
358
246
105
7
0
0
0
37
67
145
PM2.5
2009
333
260
73
0
0
0
0
31
61
94
PM2.5
2008
334
245
85
4
0
0
0
35
59
120
PM2.5
2007
343
188
130
11
9
5
0
46
86
237
PM2.5
2006
354
194
151
8
1
0
0
47
72
152
PM2.5
2005
237
139
87
11
0
0
0
43
84
148
PM2.5
2004
223
193
25
4
1
0
0
18
54
157
PM10
2003
340
304
31
3
2
0
0
18
54
163
PM10
2002
335
307
28
0
0
0
0
17
45
85
PM10
2001
342
309
32
1
0
0
0
19
47
117
PM10
2000
356
302
40
4
9
1
0
18
63
275
PM10
1999
349
343
6
0
0
0
0
14
30
62
PM10
1998
347
333
14
0
0
0
0
15
35
86
PM10
1997
353
348
5
0
0
0
0
16
31
57
PM10
1996
314
305
9
0
0
0
0
17
33
73
PM10
1995
335
327
8
0
0
0
0
16
33
67
PM10
1994
153
140
13
0
0
0
0
19
44
88
PM10
1987
39
34
5
0
0
0
0
20
51
65
PM10
1986
33
26
7
0
0
0
0
31
64
79
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 Montana with a similar median AQI in 2025
