Median AQI
41
Good
Alabama · County air quality · 2025
DeKalb County, Alabama
Median AQI 41 (Good). 77.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 41
- Median AQI
- 77.3%
- Good-air days
- 0
- Unhealthy days
- 49%
- Cleaner than US counties
DeKalb County's 2025 annual median AQI is 41 (Good), with 77.3% Good days
According to the U.S. EPA Air Quality System, DeKalb County, Alabama posted a 2025 median AQI of 41 (Good) across 365 monitored days, with 77.3% 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
- DeKalb County's 77.3% Good-day share places it cleaner than 49% 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 DeKalb County.
- 2020–2025 trend
- DeKalb County's floor-qualifying Good-day share is worsening from 2020 to 2025 (91.2% → 77.3%).
- Median AQI
- Median AQI: 41
The verdict
According to EPA Air Quality System monitoring data, DeKalb County's air is good on balance, more polluted than the median US county, a median AQI of 41 with 77.3% of 365 monitored days in the Good band, driven mainly by Ozone.
- 41
- median AQI · Good
- 77.3%
- days rated Good
- Ozone
- main pollutant
- 49%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 93.
Annual release change
What changed in the 2025 EPA annual release
- DeKalb County's Good-day share rose from 75.7% to 77.3% between the 2024 and 2025 EPA annual releases, a change of +1.6 percentage points.
Data updated August 2026
- Good · 282 d · 77.3%
- Moderate · 83 d · 22.7%
How did DeKalb County's air break down in 2025?
Across 365 monitored days, 282 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 93 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 41 (Good).
Insights: DeKalb County, Alabama. EPA monitors recorded a median Air Quality Index of 41 across 365 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 282 (77%) fell in the Good band (AQI 0–50), 83 (23%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 56, while the worst single-day peak hit 93 (Moderate). Residents averaged about 23.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (233 days), PM2.5 (132 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -13.9 points and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 93, moderate but never Unhealthy. Nearby counties show comparable readings: Baldwin (75.5% good, AQI 42); Clay (81.1% good, AQI 33); Elmore (97.9% good, AQI 34); Etowah (61.4% good, AQI 45); Jefferson (43.6% good, AQI 52); Lawrence (91.8% good, AQI 30).
Air Quality Summary
Good Days
77.3%
282 of 365 monitored days
2.3pp vs 75% target
Max AQI Recorded
93
Moderate
Health Grade
Good
90th-pct AQI 56
DeKalb County, Good days share 77.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
DeKalb 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 365 monitored days across EPA AQI categories.
Good
282
77%
Moderate
83
23%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in DeKalb County.
- Ozone · 233 days · 63.8%
- PM2.5 · 132 days · 36.2%
Health Impact Assessment
Good
DeKalb County's air quality is rated Good based on 77.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 77.3% 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 233 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in DeKalb County. Highest Good-day share: 2020 (91.2%, 332 of 364 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 332 | 32 | 0 | 0 | 37 | 91 |
| 2021 | 315 | 46 | 0 | 0 | 37 | 84 |
| 2022 | 323 | 41 | 0 | 0 | 38 | 97 |
| 2023 | 212 | 151 | 2 | 0 | 48 | 133 |
| 2024 | 277 | 89 | 0 | 0 | 43 | 87 |
| 2025 | 282 | 83 | 0 | 0 | 41 | 93 |
How does DeKalb County compare?
How DeKalb County compares
Good-day share better than typical
DeKalb County 77.3%
Armstrong County, Pennsylvania 70.5%
Typical US county 76.0%
Median AQI worse than typical
DeKalb County 41
Armstrong County, Pennsylvania 41
Typical US county 39
Unhealthy days / yr better than typical
DeKalb 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 DeKalb 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).
Middlesex County, Connecticut
77.5% Good-day share · median AQI 42
Lycoming County, Pennsylvania
77.5% Good-day share · median AQI 40
Polk County, Arkansas
77.5% Good-day share · median AQI 41
Warren County, New Jersey
77.5% Good-day share · median AQI 37
White Pine County, Nevada
77.0% Good-day share · median AQI 45
Multnomah County, Oregon
77.5% Good-day share · median AQI 37
Alabama counties on the map
Geographic containment only, other monitored counties in Alabama, independent of AQI or pollutant match.
What DeKalb 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 DeKalb County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare DeKalb County with its Alabama neighbours before drawing a conclusion about the region. All of Alabama
Based on 365 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 DeKalb County, Alabama? ▼
DeKalb County has a median Air Quality Index (AQI) of 41, rated "Good." 77.3% of monitored days (282 out of 365) had good air quality in 2025.
What is the main pollutant in DeKalb County? ▼
The primary pollutant in DeKalb County is Ozone (O3), which was the main AQI driver on 233 days (64% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does DeKalb County have? ▼
In 2025, DeKalb County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 93.
Is the air quality in DeKalb County getting better or worse? ▼
Air quality in DeKalb 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 91.2% (332 of 364 days). Lowest qualifying Good-day share: 2023 at 58.1% (212 of 365 days).
What does AQI 41 mean for health? ▼
DeKalb 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 DeKalb County compare to other counties in Alabama? ▼
DeKalb County has 77.3% good air days. Nearby counties in Alabama: Baldwin (75.5% good), Clay (81.1% good), Elmore (97.9% good), Etowah (61.4% good), Jefferson (43.6% good), Lawrence (91.8% good).
What is the 90th percentile AQI in DeKalb County? ▼
The 90th percentile AQI for DeKalb County is 56, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 93 (Moderate).
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 DeKalb County, Alabama · 2020–2025
Share this annual record
Send the source-year summary or download its ready-to-use data card.
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
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.