Median AQI
40
Good
Florida · County air quality · 2025
Seminole County, Florida
Median AQI 40 (Good). 83.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 83.5%
- Good-air days
- 0
- Unhealthy days
- 62%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Seminole County's air is good on balance, cleaner than the median US county, a median AQI of 40 with 83.5% of 272 monitored days in the Good band, driven mainly by Ozone.
- 40
- median AQI · Good
- 83.5%
- days rated Good
- Ozone
- main pollutant
- 62%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 97.
Data updated July 2026
- Good · 227 d · 83.5%
- Moderate · 45 d · 16.5%
How did Seminole County's air break down in 2025?
Across 272 monitored days, 227 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 97 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 272 days monitored. Median AQI: 40 (Good).
Insights: Seminole County, Florida. EPA monitors recorded a median Air Quality Index of 40 across 272 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 227 (83%) fell in the Good band (AQI 0–50), 45 (17%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 97 (Moderate). Residents averaged about 25.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (187 days), PM2.5 (85 days). Across the 2020–2025 trend window, good days shifted by -60 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 97, moderate but never Unhealthy. Nearby counties show comparable readings: Alachua (90.1% good, AQI 37); Baker (69.1% good, AQI 45); Bay (60.6% good, AQI 46); Brevard (89.7% good, AQI 37); Broward (72.4% good, AQI 43); Citrus (67.8% good, AQI 44).
Air Quality Summary
Good Days
83.5%
227 of 272 monitored days
8.5pp vs 75% target
Max AQI Recorded
97
Moderate
Health Grade
Good
90th-pct AQI 54
Seminole County, Good days share 83.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Seminole 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 272 monitored days across EPA AQI categories.
Good
227
83%
Moderate
45
17%
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 Seminole County.
- Ozone · 187 days · 68.8%
- PM2.5 · 85 days · 31.3%
Health Impact Assessment
Good
Seminole County's air quality is rated Good based on 83.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 83.5% of monitored days in 2025, with a median AQI of 40. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 187 of 272 monitored days.
5-Year Air Quality Trend
Air quality is improving in Seminole County. Best year: 2023 (299 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 287 | 78 | 0 | 0 | 40 | 84 |
| 2021 | 273 | 92 | 0 | 0 | 42 | 97 |
| 2022 | 288 | 75 | 0 | 0 | 42 | 87 |
| 2023 | 299 | 64 | 1 | 0 | 40 | 106 |
| 2024 | 204 | 81 | 1 | 0 | 43 | 149 |
| 2025 | 227 | 45 | 0 | 0 | 40 | 97 |
How does Seminole County compare?
How Seminole County compares
Good-day share better than US avg
Seminole County 83.5%
Alachua County, Florida 90.1%
US average 76.5%
Median AQI worse than US avg
Seminole County 40
Alachua County, Florida 37
US average 38
Unhealthy days / yr about average
Seminole County 0
Alachua County, Florida 0
US average 0
Other Counties in Florida
Air quality comparison for nearby counties in Florida.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Seminole County.
Amador County, California
AQI 40 · 84.8% good
Anne Arundel County, Maryland
AQI 40 · 87.2% good
Arlington County, Virginia
AQI 40 · 84.8% good
Bergen County, New Jersey
AQI 40 · 71.1% good
Berkeley County, West Virginia
AQI 40 · 81.1% good
Billings County, North Dakota
AQI 40 · 80.3% good
What Seminole 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 40 means for exposure. Health guidance
- See how Seminole County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Seminole County with its Florida neighbours before drawing a conclusion about the region. All of Florida
Based on 272 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 Seminole County, Florida? ▼
Seminole County has a median Air Quality Index (AQI) of 40, rated "Good." 83.5% of monitored days (227 out of 272) had good air quality in 2025.
What is the main pollutant in Seminole County? ▼
The primary pollutant in Seminole County is Ozone (O3), which was the main AQI driver on 187 days (69% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Seminole County have? ▼
In 2025, Seminole County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 97.
Is the air quality in Seminole County getting better or worse? ▼
Air quality in Seminole County is improving based on 5-year trends (2020-2025). Best year: 2023 with 299 good days. Worst year: 2024 with 204 good days.
What does AQI 40 mean for health? ▼
Seminole County's median AQI of 40 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 Seminole County compare to other counties in Florida? ▼
Seminole County has 83.5% good air days. Nearby counties in Florida: Alachua (90.1% good), Baker (69.1% good), Bay (60.6% good), Brevard (89.7% good), Broward (72.4% good), Citrus (67.8% good).
What is the 90th percentile AQI in Seminole County? ▼
The 90th percentile AQI for Seminole County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 97 (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.