Puerto Rico · County air quality · 2025
Mayagnez County, Puerto Rico
Median AQI 9 (Good). 97.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 9
- Median AQI
- 97.8%
- Good-air days
- 2
- Unhealthy days
- 98%
- Cleaner than US counties
Mayagnez County's 2025 annual median AQI is 9 (Good), with 97.8% Good days
According to the U.S. EPA Air Quality System, Mayagnez County, Puerto Rico posted a 2025 median AQI of 9 (Good) across 227 monitored days, with 97.8% rated Good and 2 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Mayagnez County's 97.8% Good-day share places it cleaner than 98% of US counties in 2025.
- Closest median-AQI peer
- Kenai Peninsula County (100.0% Good, median AQI 9) is the closest nationwide median-AQI peer to Mayagnez County.
- 2020–2025 trend
- Mayagnez County's floor-qualifying Good-day share is improving from 2020 to 2025 (83.9% → 98.7%).
- Median AQI
- Median AQI: 9
According to the 2025 EPA AQS county release on PlainAirData, Mayagnez County, Puerto Rico ranks #7 of 951 by median AQI (9) and #22 by good-day share (97.8%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Mayagnez County's peak single-day AQI rose from 39 to 350 between the 2024 and 2025 EPA annual releases, a change of +311 points.
- Mayagnez County's Good-day share fell from 100.0% to 97.8% between the 2024 and 2025 EPA annual releases, a change of -2.2 percentage points.
Data updated August 2026
- Good · 222 d · 97.8%
- Moderate · 1 d · 0.4%
- USG · 2 d · 0.9%
- Very Unhealthy · 1 d · 0.4%
- Hazardous · 1 d · 0.4%
How did Mayagnez County's air break down in 2025?
Across 227 monitored days, 222 fell in the Good band (AQI 0–50) and 2 reached Unhealthy or worse. The worst single day peaked at AQI 350 (Hazardous).
EPA AQS →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Mayagnez County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Mayagnez County's Good-day share is 97.8% - cleaner than 98% of that comparison set.
Mayagnez County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
97.8% Cleaner than 98% higher than 98% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Mayagnez County.
- Ozone · 227 days · 100.0%
2024 daily-monitor rhythm in Mayagnez County
Month-by-month median AQI from EPA day-level county monitors (341 reported days in 2024). Jan posted the highest typical readings (median AQI 22, peak 30); Sep was cleanest at median 1. Summer months (Jun–Aug) averaged median AQI 6 vs 15 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,600 daily readings show a recurring local pattern: Sep has the highest matched-month median AQI (39), while Dec is lowest (21). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Mayagnez County's air quality is rated Excellent based on 97.8% good air days. There were 2 unhealthy days in 2025 when outdoor activity should be limited.
Air quality posed significant health risk in 2025. Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, pregnant women, and adults over 65, should monitor AirNow.gov alerts and limit outdoor activity on Unhealthy (AQI 151+) and Very Unhealthy (201+) days. Peak readings reached AQI 350, well into the Hazardous range.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is Ozone, driving AQI on 227 of 227 monitored days.
5-Year Air Quality Trend
Air quality is improving in Mayagnez County. Highest Good-day share: 2024 (100.0%, 341 of 341 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 266 | 49 | 1 | 1 | 22 | 396 |
| 2021 | 231 | 101 | 2 | 0 | 38 | 142 |
| 2022 | 235 | 81 | 4 | 1 | 38 | 155 |
| 2023 | 254 | 31 | 0 | 0 | 25 | 64 |
| 2024 | 341 | 0 | 0 | 0 | 11 | 39 |
| 2025 | 222 | 1 | 2 | 0 | 9 | 350 |
How does Mayagnez County compare?
How Mayagnez County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Mayagnez County, Puerto Rico · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.