Hillsborough, Florida vs Miami-Dade, Florida Air Quality
Side-by-side air quality comparison using 10 years of EPA monitoring data. Miami-Dade, Florida has the edge with an Air Quality Grade of B (68/100).
| Metric | Hillsborough, Florida | Miami-Dade, Florida |
|---|---|---|
| Air Quality Grade | C (60/100) | B (68/100) |
| Current Median AQI | 51 (Moderate) | 48 (Good) |
| 5-Year Average AQI | 51 | 45 |
| 10-Year Trend | → Stable (-1) | ↓ Improving (-4) |
| Unhealthy Days/Year | 3 | 2 |
| Primary Pollutant | Fine Particulate Matter (PM2.5) | Fine Particulate Matter (PM2.5) |
Side-by-Side Analysis
Miami-Dade, Florida outperforms Hillsborough, Florida on overall air quality with a Grade B (68/100) versus C (60/100). Miami-Dade, Florida's 5-year median AQI of 45 sits in the "Good" range, while Hillsborough, Florida averages 51 ("Moderate") — a 5-point gap that shows up consistently in year-over-year readings, not just in a single year.
The two cities are moving in opposite directions: Hillsborough, Florida is stable (-0.1 AQI/yr) while Miami-Dade, Florida is improving (-0.8 AQI/yr). Over time, today's ranking may flip if these trends hold.
What's in the Air
Both cities share the same dominant pollutant: Fine Particulate Matter (PM2.5). These cities' dominant issue is fine particulate matter — typically driven by combustion (vehicles, wildfire smoke, industry, residential wood burning). PM2.5 is the air pollutant most strongly linked to long-term cardiovascular and respiratory disease because the particles penetrate the bloodstream.
Health Implications
Over a 5-year window, Hillsborough, Florida averages roughly 3 unhealthy air days per year (AQI above 100, where sensitive groups should limit outdoor exertion) versus 2 for Miami-Dade, Florida. The two cities offer comparable counts of unhealthy days, suggesting that day-to-day exposure planning would look similar for residents of either. For long-term residents, the cleaner-air city is associated with measurably better outcomes on respiratory disease, cardiovascular events, and life expectancy — Harvard cohort research consistently finds 0.5 to 1.0 years of additional life expectancy for each 10-µg/m³ reduction in long-term PM2.5 exposure.
Frequently Asked Questions
Miami-Dade, Florida has better air quality with a Grade B (68/100) compared to Hillsborough, Florida's Grade C (60/100). Miami-Dade, Florida has a current median AQI of 48 and is improving over the past decade.
Hillsborough, Florida averages 3 unhealthy air days per year (5-year average), while Miami-Dade, Florida averages 2. Unhealthy days are those when AQI exceeds 100 and sensitive groups should limit outdoor activity.
Hillsborough, Florida's primary pollutant is Fine Particulate Matter (PM2.5), while Miami-Dade, Florida's is Fine Particulate Matter (PM2.5). Both cities share the same dominant pollutant.
Source: EPA Outdoor Air Quality Data, 2026.
Comparing entity A and entity B on U.S. air quality and AQI history requires lining up the underlying EPA Air Quality System data data side by side. The table above runs the comparison on the canonical fields; the narrative below identifies the factor or factors that drive the most meaningful difference between the two.
Practical use of the comparison: read the data above, then drill into the individual entity A and entity B detail pages for the underlying breakdown. A pairwise comparison answers the relative question; the per-entity pages answer the absolute question.