Median AQI
30
Good
Puerto Rico · County air quality · 2025
Guaynabo County, Puerto Rico
Median AQI 30 (Good). 86.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 30
- Median AQI
- 86.0%
- Good-air days
- 0
- Unhealthy days
- 68%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Guaynabo County's air is good on balance, cleaner than the median US county, a median AQI of 30 with 86.0% of 57 monitored days in the Good band, driven mainly by PM2.5.
- 30
- median AQI · Good
- 86.0%
- days rated Good
- PM2.5
- main pollutant
- 68%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 66.
Data updated July 2026
- Good · 49 d · 86.0%
- Moderate · 8 d · 14.0%
How did Guaynabo County's air break down in 2025?
Across 57 monitored days, 49 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 66 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 57 days monitored. Median AQI: 30 (Good).
Insights: Guaynabo County, Puerto Rico. EPA monitors recorded a median Air Quality Index of 30 across 57 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 49 (86%) fell in the Good band (AQI 0–50), 8 (14%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 59, while the worst single-day peak hit 66 (Moderate). Residents averaged about 25.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (57 days). Across the 2020–2025 trend window, good days shifted by -19 and the median AQI moved +1 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 66, moderate but never Unhealthy. Nearby counties show comparable readings: Bayamon (88.5% good, AQI 29); Caguas (94.3% good, AQI 3); Catano (64.6% good, AQI 44); Fajardo (85.7% good, AQI 29); Guayama (100.0% good, AQI 18); Mayagnez (96.9% good, AQI 12).
Air Quality Summary
Good Days
86.0%
49 of 57 monitored days
11.0pp vs 75% target
Max AQI Recorded
66
Moderate
Health Grade
Good
90th-pct AQI 59
Guaynabo County, Good days share 86.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Guaynabo 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 57 monitored days across EPA AQI categories.
Good
49
86%
Moderate
8
14%
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 Guaynabo County.
- PM2.5 · 57 days · 100.0%
Health Impact Assessment
Good
Guaynabo County's air quality is rated Good based on 86.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 86.0% of monitored days in 2025, with a median AQI of 30. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 57 of 57 monitored days.
5-Year Air Quality Trend
Air quality is improving in Guaynabo County. Best year: 2024 (91 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 68 | 15 | 0 | 0 | 29 | 75 |
| 2021 | 86 | 33 | 0 | 0 | 33 | 77 |
| 2022 | 81 | 13 | 0 | 0 | 29 | 80 |
| 2023 | 82 | 25 | 0 | 0 | 32 | 74 |
| 2024 | 91 | 24 | 0 | 0 | 31 | 81 |
| 2025 | 49 | 8 | 0 | 0 | 30 | 66 |
How does Guaynabo County compare?
How Guaynabo County compares
Good-day share better than US avg
Guaynabo County 86.0%
Bayamon County, Puerto Rico 88.5%
US average 76.5%
Median AQI better than US avg
Guaynabo County 30
Bayamon County, Puerto Rico 29
US average 38
Unhealthy days / yr about average
Guaynabo County 0
Bayamon County, Puerto Rico 0
US average 0
Other Counties in Puerto Rico
Air quality comparison for nearby counties in Puerto Rico.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Guaynabo County.
Canyon County, Idaho
AQI 30 · 87.2% good
Hawaii County, Hawaii
AQI 30 · 81.1% good
Lynchburg City County, Virginia
AQI 30 · 84.2% good
Putnam County, Tennessee
AQI 30 · 88.6% good
Salem City County, Virginia
AQI 30 · 79.6% good
Whatcom County, Washington
AQI 30 · 96.6% good
What Guaynabo 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 30 means for exposure. Health guidance
- See how Guaynabo County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Guaynabo County with its Puerto Rico neighbours before drawing a conclusion about the region. All of Puerto Rico
Based on 57 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 Guaynabo County, Puerto Rico? ▼
Guaynabo County has a median Air Quality Index (AQI) of 30, rated "Good." 86.0% of monitored days (49 out of 57) had good air quality in 2025.
What is the main pollutant in Guaynabo County? ▼
The primary pollutant in Guaynabo County is Fine Particles (PM2.5), which was the main AQI driver on 57 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Guaynabo County have? ▼
In 2025, Guaynabo County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 66.
Is the air quality in Guaynabo County getting better or worse? ▼
Air quality in Guaynabo County is improving based on 5-year trends (2020-2025). Best year: 2024 with 91 good days. Worst year: 2025 with 49 good days.
What does AQI 30 mean for health? ▼
Guaynabo County's median AQI of 30 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 Guaynabo County compare to other counties in Puerto Rico? ▼
Guaynabo County has 86.0% good air days. Nearby counties in Puerto Rico: Bayamon (88.5% good), Caguas (94.3% good), Catano (64.6% good), Fajardo (85.7% good), Guayama (100.0% good), Mayagnez (96.9% good).
What is the 90th percentile AQI in Guaynabo County? ▼
The 90th percentile AQI for Guaynabo County is 59, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 66 (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.