Daily Air Quality Index summaries from EPA monitors in Harrison, Mississippi, 1999–2025.
69%
Good days in 2025
43
Median daily AQI, 2025
0
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 Harrison, Mississippi on 365 days. 252 of those days (69%) were in the Good range, and the median daily AQI was 43. That median is about the same as the typical monitored county in Mississippi (median 43 across 10 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 rose: an average of 29% in 1999–2001 versus 60% in 2023–2025.
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
66%
Ozone
123
34%
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
252
113
0
0
0
0
43
62
97
PM2.5
2024
361
239
117
4
1
0
0
44
62
157
PM2.5
2023
361
166
193
2
0
0
0
51
68
105
PM2.5
2022
365
211
154
0
0
0
0
46
62
100
PM2.5
2021
359
221
138
0
0
0
0
45
58
87
PM2.5
2020
352
179
172
1
0
0
0
49
63
101
PM2.5
2019
363
201
162
0
0
0
0
47
63
97
PM2.5
2018
364
223
138
3
0
0
0
45
63
115
PM2.5
2017
361
232
128
1
0
0
0
44
60
105
PM2.5
2016
359
256
103
0
0
0
0
44
57
97
PM2.5
2015
363
223
138
2
0
0
0
44
63
115
PM2.5
2014
361
184
172
5
0
0
0
50
63
119
PM2.5
2013
357
212
145
0
0
0
0
47
61
90
PM2.5
2012
362
189
168
5
0
0
0
49
67
136
PM2.5
2011
361
142
212
7
0
0
0
53
74
129
PM2.5
2010
362
133
219
10
0
0
0
54
73
136
PM2.5
2009
317
116
196
5
0
0
0
53
67
150
PM2.5
2008
324
126
187
10
1
0
0
54
76
159
PM2.5
2007
365
104
242
17
2
0
0
56
80
164
PM2.5
2006
365
89
251
22
3
0
0
58
92
169
PM2.5
2005
360
76
252
29
3
0
0
60
100
156
PM2.5
2004
356
100
237
17
2
0
0
56
87
164
PM2.5
2003
364
109
232
20
3
0
0
55
87
182
PM2.5
2002
360
132
217
10
1
0
0
53
74
161
PM2.5
2001
360
91
251
16
2
0
0
57
82
159
PM2.5
2000
364
87
230
40
7
0
0
59
108
197
PM2.5
1999
259
98
123
32
6
0
0
57
115
197
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 Mississippi with a similar median AQI in 2025
