Median AQI
41
Good
Maryland · County air quality · 2025
Cecil County, Maryland
Median AQI 41 (Good). 79.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 41
- Median AQI
- 79.8%
- Good-air days
- 0
- Unhealthy days
- 56%
- Cleaner than US counties
Cecil County's 2025 annual median AQI is 41 (Good), with 79.8% Good days
According to the U.S. EPA Air Quality System, Cecil County, Maryland posted a 2025 median AQI of 41 (Good) across 361 monitored days, with 79.8% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Cecil County's 79.8% Good-day share places it cleaner than 56% of US counties in 2025.
- Closest median-AQI peer
- Armstrong County (70.5% Good, median AQI 41) is the closest nationwide median-AQI peer to Cecil County.
- 2020–2025 trend
- Cecil County's floor-qualifying Good-day share is worsening from 2020 to 2025 (86.6% → 79.8%).
- Median AQI
- Median AQI: 41
The verdict
According to EPA Air Quality System monitoring data, Cecil County's air is good on balance, cleaner than the median US county, a median AQI of 41 with 79.8% of 361 monitored days in the Good band, driven mainly by Ozone.
- 41
- median AQI · Good
- 79.8%
- days rated Good
- Ozone
- main pollutant
- 56%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 129.
Annual release change
What changed in the 2025 EPA annual release
- Cecil County's Good-day share rose from 65.6% to 79.8% between the 2024 and 2025 EPA annual releases, a change of +14.2 percentage points.
- Cecil County's median AQI fell from 44 to 41 between the 2024 and 2025 EPA annual releases, a change of -3 points.
Data updated August 2026
- Good · 288 d · 79.8%
- Moderate · 71 d · 19.7%
- USG · 2 d · 0.6%
How did Cecil County's air break down in 2025?
Across 361 monitored days, 288 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 129 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 361 days monitored. Median AQI: 41 (Good).
Insights: Cecil County, Maryland. EPA monitors recorded a median Air Quality Index of 41 across 361 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 288 (80%) fell in the Good band (AQI 0–50), 71 (20%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 60, while the worst single-day peak hit 129 (USG). Residents averaged about 23.9 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (195 days), PM2.5 (166 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -6.8 points and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 129, usg but never Unhealthy. Nearby counties show comparable readings: Anne Arundel (87.6% good, AQI 40); Baltimore (64.7% good, AQI 45); Baltimore (City) (68.1% good, AQI 43); Calvert (94.6% good, AQI 38); Carroll (90.3% good, AQI 38); Charles (92.4% good, AQI 38).
Air Quality Summary
Good Days
79.8%
288 of 361 monitored days
4.8pp vs 75% target
Max AQI Recorded
129
USG
Health Grade
Good
90th-pct AQI 60
Cecil County, Good days share 79.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Cecil County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 361 monitored days across EPA AQI categories.
Good
288
80%
Moderate
71
20%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Cecil County.
- Ozone · 195 days · 54.0%
- PM2.5 · 166 days · 46.0%
Health Impact Assessment
Good
Cecil County's air quality is rated Good based on 79.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 79.8% of monitored days in 2025, with a median AQI of 41. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 195 of 361 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Cecil County. Highest Good-day share: 2020 (86.6%, 309 of 357 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 309 | 48 | 0 | 0 | 38 | 97 |
| 2021 | 235 | 119 | 4 | 0 | 44 | 118 |
| 2022 | 267 | 93 | 1 | 0 | 43 | 101 |
| 2023 | 266 | 88 | 2 | 4 | 42 | 190 |
| 2024 | 236 | 121 | 3 | 0 | 44 | 126 |
| 2025 | 288 | 71 | 2 | 0 | 41 | 129 |
How does Cecil County compare?
How Cecil County compares
Good-day share better than typical
Cecil County 79.8%
Armstrong County, Pennsylvania 70.5%
Typical US county 76.0%
Median AQI worse than typical
Cecil County 41
Armstrong County, Pennsylvania 41
Typical US county 39
Unhealthy days / yr better than typical
Cecil County 0
Armstrong County, Pennsylvania 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Cecil County (41), not geographic neighbors.
Armstrong County, Pennsylvania
Median AQI 41 · 70.5% Good-day share
Benewah County, Idaho
Median AQI 41 · 63.4% Good-day share
Berrien County, Michigan
Median AQI 41 · 80.9% Good-day share
Callaway County, Missouri
Median AQI 41 · 89.6% Good-day share
Cambria County, Pennsylvania
Median AQI 41 · 74.5% Good-day share
Cass County, Missouri
Median AQI 41 · 77.6% Good-day share
Same primary pollutant: Ozone
Ozone led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Monongalia County, West Virginia
79.8% Good-day share · median AQI 42
Grand County, Colorado
79.8% Good-day share · median AQI 44
Dunn County, North Dakota
79.7% Good-day share · median AQI 39
Nevada County, California
79.8% Good-day share · median AQI 42
Kiowa County, Oklahoma
79.7% Good-day share · median AQI 43
Rock County, Wisconsin
79.9% Good-day share · median AQI 42
Maryland counties on the map
Geographic containment only, other monitored counties in Maryland, independent of AQI or pollutant match.
What Cecil County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 41 means for exposure. Health guidance
- See how Cecil County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Cecil County with its Maryland neighbours before drawing a conclusion about the region. All of Maryland
Based on 361 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Cecil County, Maryland? ▼
Cecil County has a median Air Quality Index (AQI) of 41, rated "Good." 79.8% of monitored days (288 out of 361) had good air quality in 2025.
What is the main pollutant in Cecil County? ▼
The primary pollutant in Cecil County is Ozone (O3), which was the main AQI driver on 195 days (54% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Cecil County have? ▼
In 2025, Cecil County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 129.
Is the air quality in Cecil County getting better or worse? ▼
Air quality in Cecil County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 86.6% (309 of 357 days). Lowest qualifying Good-day share: 2024 at 65.6% (236 of 360 days).
What does AQI 41 mean for health? ▼
Cecil County's median AQI of 41 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Cecil County compare to other counties in Maryland? ▼
Cecil County has 79.8% good air days. Nearby counties in Maryland: Anne Arundel (87.6% good), Baltimore (64.7% good), Baltimore (City) (68.1% good), Calvert (94.6% good), Carroll (90.3% good), Charles (92.4% good).
What is the 90th percentile AQI in Cecil County? ▼
The 90th percentile AQI for Cecil County is 60, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 129 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Cecil County, Maryland · 2020–2025
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Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.