Daily Air Quality Index summaries from EPA monitors in Calvert, Maryland, 1996–2025.
95%
Good days in 2025
38
Median daily AQI, 2025
0
Days above 100 in 2025
240
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Calvert, Maryland on 240 days. 227 of those days (95%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in Maryland (median 39.5 across 16 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 240 days. Across the years with fuller monitoring, the share of Good days rose: an average of 54% in 1996–1998 versus 89% in 2023–2025.
EPA did not report an AQI for every day of 2025 here (240 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.
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
Ozone
240
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
240
227
13
0
0
0
0
38
48
77
Ozone
2024
237
203
33
1
0
0
0
41
51
108
Ozone
2023
238
206
31
1
0
0
0
42
54
101
Ozone
2022
239
225
14
0
0
0
0
39
47
74
Ozone
2021
223
205
17
1
0
0
0
39
49
105
Ozone
2020
238
235
3
0
0
0
0
35
44
67
Ozone
2019
232
214
18
0
0
0
0
39
49
71
Ozone
2018
243
209
33
1
0
0
0
39
58
147
Ozone
2017
240
199
40
1
0
0
0
43
61
108
Ozone
2016
214
165
46
3
0
0
0
42
67
115
Ozone
2015
206
145
61
0
0
0
0
44
71
93
Ozone
2014
213
156
54
3
0
0
0
44
71
105
Ozone
2013
211
175
33
3
0
0
0
42
61
105
Ozone
2012
211
142
54
13
1
1
0
45
90
206
Ozone
2011
209
148
47
11
3
0
0
44
84
169
Ozone
2010
210
120
78
8
4
0
0
47
90
182
Ozone
2009
204
158
44
2
0
0
0
42
67
119
Ozone
2008
190
112
64
13
1
0
0
45
93
154
Ozone
2007
202
106
73
22
1
0
0
50
101
159
Ozone
2006
214
131
63
17
3
0
0
46
100
161
Ozone
2005
194
129
48
15
2
0
0
44
97
166
Ozone
2001
214
143
50
17
4
0
0
44
100
164
Ozone
2000
210
138
51
16
5
0
0
44
101
182
Ozone
1999
208
121
54
23
10
0
0
47
129
192
Ozone
1998
213
114
61
28
10
0
0
48
122
177
Ozone
1997
201
107
73
17
4
0
0
49
101
177
Ozone
1996
155
84
46
24
1
0
0
49
115
151
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 Maryland with a similar median AQI in 2025
