Washington County, Rhode Island air quality history
Daily Air Quality Index summaries from EPA monitors in Washington, Rhode Island, 1997–2025.
83%
Good days in 2025
37
Median daily AQI, 2025
4
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 Washington, Rhode Island on 365 days. 302 of those days (83%) were in the Good range, and the median daily AQI was 37. That median is about the same as the typical monitored county in Rhode Island (median 37 across 3 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 186 days. Across the years with fuller monitoring, the share of Good days rose: an average of 72% in 1998–2000 versus 84% 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)
186
51%
Ozone
179
49%
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
302
59
4
0
0
0
37
56
129
PM2.5
2024
358
316
39
3
0
0
0
35
52
147
Ozone
2023
355
287
58
10
0
0
0
40
58
140
PM2.5
2022
356
313
39
3
1
0
0
36
51
164
Ozone
2021
358
306
50
2
0
0
0
36
52
143
PM2.5
2020
366
327
37
1
1
0
0
35
51
154
Ozone
2019
352
317
33
2
0
0
0
38
50
126
Ozone
2018
361
311
45
5
0
0
0
35
54
115
PM2.5
2017
362
312
45
4
1
0
0
35
52
151
Ozone
2016
361
302
55
3
1
0
0
38
55
151
Ozone
2015
361
265
89
7
0
0
0
42
61
147
PM2.5
2014
363
328
34
1
0
0
0
37
50
101
Ozone
2013
360
293
58
8
1
0
0
39
57
169
Ozone
2012
299
231
60
6
2
0
0
41
61
179
Ozone
2011
230
193
30
7
0
0
0
37
77
147
Ozone
2010
209
164
38
7
0
0
0
43
77
143
Ozone
2009
183
152
28
3
0
0
0
41
61
115
Ozone
2008
180
128
46
4
2
0
0
44
74
159
Ozone
2007
181
136
31
12
2
0
0
42
87
187
Ozone
2006
183
125
42
13
2
1
0
44
90
226
Ozone
2005
179
129
31
14
5
0
0
44
105
169
Ozone
2004
180
134
41
1
3
1
0
41
80
205
Ozone
2003
182
125
44
5
7
1
0
43
93
208
Ozone
2002
241
145
70
18
7
1
0
46
112
207
Ozone
2001
232
141
69
12
8
2
0
45
93
219
Ozone
2000
238
156
72
8
1
1
0
42
77
222
Ozone
1999
198
141
40
7
8
2
0
41
93
214
Ozone
1998
206
163
35
7
1
0
0
40
74
161
Ozone
1997
74
54
13
4
3
0
0
41
100
179
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 Rhode Island with a similar median AQI in 2025
