Median AQI
36
Good
Georgia · County air quality · 2025
Cobb County, Georgia
Median AQI 36 (Good). 92.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 36
- Median AQI
- 92.5%
- Good-air days
- 0
- Unhealthy days
- 82%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Cobb County's air is good on balance, cleaner than most US counties, a median AQI of 36 with 92.5% of 214 monitored days in the Good band, driven mainly by Ozone.
- 36
- median AQI · Good
- 92.5%
- days rated Good
- Ozone
- main pollutant
- 82%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 74.
Data updated July 2026
- Good · 198 d · 92.5%
- Moderate · 16 d · 7.5%
How did Cobb County's air break down in 2025?
Across 214 monitored days, 198 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 74 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 214 days monitored. Median AQI: 36 (Good).
Insights: Cobb County, Georgia. EPA monitors recorded a median Air Quality Index of 36 across 214 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 198 (93%) fell in the Good band (AQI 0–50), 16 (7%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 47, while the worst single-day peak hit 74 (Moderate). Residents averaged about 27.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (208 days), PM2.5 (6 days). Across the 2020–2025 trend window, good days shifted by -45 and the median AQI moved +0 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 74, moderate but never Unhealthy. Nearby counties show comparable readings: Bibb (49.5% good, AQI 51); Charlton (79.0% good, AQI 24); Chatham (66.7% good, AQI 44); Clarke (66.7% good, AQI 44); Clayton (53.1% good, AQI 49); Coffee (69.1% good, AQI 44).
Air Quality Summary
Good Days
92.5%
198 of 214 monitored days
17.5pp vs 75% target
Max AQI Recorded
74
Moderate
Health Grade
Excellent
90th-pct AQI 47
Cobb County, Good days share 92.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Cobb 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 214 monitored days across EPA AQI categories.
Good
198
93%
Moderate
16
7%
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 Cobb County.
- Ozone · 208 days · 97.2%
- PM2.5 · 6 days · 2.8%
Health Impact Assessment
Excellent
Cobb County's air quality is rated Excellent based on 92.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 92.5% of monitored days in 2025, with a median AQI of 36. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 208 of 214 monitored days.
5-Year Air Quality Trend
Air quality is improving in Cobb County. Best year: 2020 (243 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 243 | 42 | 0 | 0 | 36 | 91 |
| 2021 | 218 | 67 | 0 | 0 | 41 | 80 |
| 2022 | 231 | 53 | 1 | 0 | 40 | 105 |
| 2023 | 215 | 105 | 3 | 0 | 43 | 125 |
| 2024 | 202 | 162 | 0 | 0 | 48 | 86 |
| 2025 | 198 | 16 | 0 | 0 | 36 | 74 |
How does Cobb County compare?
How Cobb County compares
Good-day share better than US avg
Cobb County 92.5%
Bibb County, Georgia 49.5%
US average 76.5%
Median AQI better than US avg
Cobb County 36
Bibb County, Georgia 51
US average 38
Unhealthy days / yr about average
Cobb County 0
Bibb County, Georgia 0
US average 0
Other Counties in Georgia
Air quality comparison for nearby counties in Georgia.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Cobb County.
Aroostook County, Maine
AQI 36 · 84.1% good
Berkeley County, South Carolina
AQI 36 · 92.2% good
Carter County, Kentucky
AQI 36 · 89.8% good
Claiborne County, Tennessee
AQI 36 · 96.3% good
Clark County, Illinois
AQI 36 · 92.1% good
Fauquier County, Virginia
AQI 36 · 97.2% good
What Cobb 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 36 means for exposure. Health guidance
- See how Cobb County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Cobb County with its Georgia neighbours before drawing a conclusion about the region. All of Georgia
Based on 214 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Cobb County, Georgia? ▼
Cobb County has a median Air Quality Index (AQI) of 36, rated "Good." 92.5% of monitored days (198 out of 214) had good air quality in 2025.
What is the main pollutant in Cobb County? ▼
The primary pollutant in Cobb County is Ozone (O3), which was the main AQI driver on 208 days (97% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Cobb County have? ▼
In 2025, Cobb County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 74.
Is the air quality in Cobb County getting better or worse? ▼
Air quality in Cobb County is improving based on 5-year trends (2020-2025). Best year: 2020 with 243 good days. Worst year: 2025 with 198 good days.
What does AQI 36 mean for health? ▼
Cobb County's median AQI of 36 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Cobb County compare to other counties in Georgia? ▼
Cobb County has 92.5% good air days. Nearby counties in Georgia: Bibb (49.5% good), Charlton (79.0% good), Chatham (66.7% good), Clarke (66.7% good), Clayton (53.1% good), Coffee (69.1% good).
What is the 90th percentile AQI in Cobb County? ▼
The 90th percentile AQI for Cobb County is 47, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 74 (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.
Every figure on PlainAir 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.