Median AQI
51
Moderate
Florida · County air quality · 2025
Hillsborough County, Florida
Median AQI 51 (Moderate). 49.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 51
- Median AQI
- 49.3%
- Good-air days
- 0
- Unhealthy days
- 6%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Hillsborough County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 51 with 49.3% of 274 monitored days in the Good band, driven mainly by PM2.5.
- 51
- median AQI · Moderate
- 49.3%
- days rated Good
- PM2.5
- main pollutant
- 6%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 122.
Data updated July 2026
- Good · 135 d · 49.3%
- Moderate · 137 d · 50.0%
- USG · 2 d · 0.7%
How did Hillsborough County's air break down in 2025?
Across 274 monitored days, 135 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 122 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 274 days monitored. Median AQI: 51 (Moderate).
Insights: Hillsborough County, Florida. EPA monitors recorded a median Air Quality Index of 51 across 274 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 135 (49%) fell in the Good band (AQI 0–50), 137 (50%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 122 (USG). Residents averaged about 14.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (174 days), Ozone (95 days), PM10 (3 days), NO2 (1 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -41 and the median AQI moved -1 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 122, usg 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
49.3%
135 of 274 monitored days
-25.7pp vs 75% target
Max AQI Recorded
122
USG
Health Grade
Poor
90th-pct AQI 64
Hillsborough County, Good days share 49.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Hillsborough 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 274 monitored days across EPA AQI categories.
Good
135
49%
Moderate
137
50%
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 Hillsborough County.
- PM2.5 · 174 days · 63.5%
- Ozone · 95 days · 34.7%
- PM10 · 3 days · 1.1%
- NO₂ · 1 days · 0.4%
- CO · 1 days · 0.4%
Health Impact Assessment
Poor
Hillsborough County's air quality is rated Poor based on 49.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 49.3% of monitored days in 2025, with a median AQI of 51. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 174 of 274 monitored days.
5-Year Air Quality Trend
Air quality is stable in Hillsborough County. Best year: 2024 (190 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 176 | 187 | 3 | 0 | 52 | 112 |
| 2021 | 167 | 197 | 1 | 0 | 51 | 129 |
| 2022 | 175 | 189 | 1 | 0 | 51 | 126 |
| 2023 | 156 | 206 | 3 | 0 | 51 | 114 |
| 2024 | 190 | 168 | 4 | 0 | 50 | 143 |
| 2025 | 135 | 137 | 2 | 0 | 51 | 122 |
How does Hillsborough County compare?
How Hillsborough County compares
Good-day share worse than US avg
Hillsborough County 49.3%
Alachua County, Florida 90.1%
US average 76.5%
Median AQI worse than US avg
Hillsborough County 51
Alachua County, Florida 37
US average 38
Unhealthy days / yr about average
Hillsborough 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 Hillsborough County.
Arapahoe County, Colorado
AQI 51 · 47.3% good
Bibb County, Georgia
AQI 51 · 49.5% good
East Baton Rouge County, Louisiana
AQI 51 · 49.3% good
Eddy County, New Mexico
AQI 51 · 46.9% good
Jefferson County, Colorado
AQI 51 · 46.5% good
Mecklenburg County, North Carolina
AQI 51 · 49.2% good
What Hillsborough 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 51 means for exposure. Health guidance
- See how Hillsborough County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Hillsborough County with its Florida neighbours before drawing a conclusion about the region. All of Florida
Based on 274 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 Hillsborough County, Florida? ▼
Hillsborough County has a median Air Quality Index (AQI) of 51, rated "Moderate." 49.3% of monitored days (135 out of 274) had good air quality in 2025.
What is the main pollutant in Hillsborough County? ▼
The primary pollutant in Hillsborough County is Fine Particles (PM2.5), which was the main AQI driver on 174 days (64% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Hillsborough County have? ▼
In 2025, Hillsborough County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 122.
Is the air quality in Hillsborough County getting better or worse? ▼
Air quality in Hillsborough County is stable based on 5-year trends (2020-2025). Best year: 2024 with 190 good days. Worst year: 2025 with 135 good days.
What does AQI 51 mean for health? ▼
Hillsborough County's median AQI of 51 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Hillsborough County compare to other counties in Florida? ▼
Hillsborough County has 49.3% 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 Hillsborough County? ▼
The 90th percentile AQI for Hillsborough County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 122 (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.
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.