Median AQI
49
Good
Florida · County air quality · 2025
Hamilton County, Florida
Median AQI 49 (Good). 54.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 49
- Median AQI
- 54.2%
- Good-air days
- 0
- Unhealthy days
- 9%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Hamilton County's air is good on balance, among the most polluted counties nationally, a median AQI of 49 with 54.2% of 260 monitored days in the Good band, driven mainly by PM2.5.
- 49
- median AQI · Good
- 54.2%
- days rated Good
- PM2.5
- main pollutant
- 9%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 72.
Data updated July 2026
- Good · 141 d · 54.2%
- Moderate · 119 d · 45.8%
How did Hamilton County's air break down in 2025?
Across 260 monitored days, 141 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 72 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 260 days monitored. Median AQI: 49 (Good).
Insights: Hamilton County, Florida. EPA monitors recorded a median Air Quality Index of 49 across 260 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 141 (54%) fell in the Good band (AQI 0–50), 119 (46%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 58, while the worst single-day peak hit 72 (Moderate). Residents averaged about 16.3 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (260 days). Across the 2020–2025 trend window, good days shifted by -49 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 72, 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
54.2%
141 of 260 monitored days
-20.8pp vs 75% target
Max AQI Recorded
72
Moderate
Health Grade
Moderate
90th-pct AQI 58
Hamilton County, Good days share 54.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Hamilton 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 260 monitored days across EPA AQI categories.
Good
141
54%
Moderate
119
46%
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 Hamilton County.
- PM2.5 · 260 days · 100.0%
Health Impact Assessment
Moderate
Hamilton County's air quality is rated Moderate based on 54.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 54.2% of monitored days in 2025, with a median AQI of 49. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 260 of 260 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Hamilton County. Best year: 2024 (215 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 190 | 106 | 1 | 1 | 46 | 155 |
| 2021 | 207 | 129 | 0 | 0 | 46 | 69 |
| 2022 | 165 | 129 | 0 | 0 | 47 | 73 |
| 2023 | 191 | 127 | 0 | 0 | 46 | 89 |
| 2024 | 215 | 104 | 0 | 0 | 44 | 75 |
| 2025 | 141 | 119 | 0 | 0 | 49 | 72 |
How does Hamilton County compare?
How Hamilton County compares
Good-day share worse than US avg
Hamilton County 54.2%
Alachua County, Florida 90.1%
US average 76.5%
Median AQI worse than US avg
Hamilton County 49
Alachua County, Florida 37
US average 38
Unhealthy days / yr about average
Hamilton 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 Hamilton County.
Allegheny County, Pennsylvania
AQI 49 · 51.6% good
Arkansas County, Arkansas
AQI 49 · 51.6% good
Ashley County, Arkansas
AQI 49 · 53.9% good
Clayton County, Georgia
AQI 49 · 53.1% good
Cleveland County, Oklahoma
AQI 49 · 53.7% good
Dewey County, Oklahoma
AQI 49 · 56.6% good
What Hamilton County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 49 means for exposure. Health guidance
- See how Hamilton County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Hamilton County with its Florida neighbours before drawing a conclusion about the region. All of Florida
Based on 260 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 Hamilton County, Florida? ▼
Hamilton County has a median Air Quality Index (AQI) of 49, rated "Good." 54.2% of monitored days (141 out of 260) had good air quality in 2025.
What is the main pollutant in Hamilton County? ▼
The primary pollutant in Hamilton County is Fine Particles (PM2.5), which was the main AQI driver on 260 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Hamilton County have? ▼
In 2025, Hamilton County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 72.
Is the air quality in Hamilton County getting better or worse? ▼
Air quality in Hamilton County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 215 good days. Worst year: 2025 with 141 good days.
What does AQI 49 mean for health? ▼
Hamilton County's median AQI of 49 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 Hamilton County compare to other counties in Florida? ▼
Hamilton County has 54.2% 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 Hamilton County? ▼
The 90th percentile AQI for Hamilton County is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 72 (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.