Bad Air Days in Caguas, Puerto Rico: 1 a Year
1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 646 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (13% particle days).
When the bad days come in Caguas
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in August and October and February and July and September and December. Averaged over 2016 to 2025.
What actually helps here
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
The record for Caguas
The worst recent year was 2016, with 1 bad day on 11 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2024-07-23 | 174 | PM2.5 |
| 2019-10-09 | 114 | NO2 |
| 2016-12-22 | 112 | NO2 |
| 2019-10-21 | 110 | NO2 |
| 2019-08-12 | 107 | NO2 |
Most days, not the worst ones
Across 2,470 monitored days from 2016 to 2025, the air in Caguas rated Good on 94% of them, more often than the 72% typical of monitored counties, and Moderate on 5%. The median day sat at AQI 10; one day in ten went above 36.
The pollutant setting the AQI on an ordinary day here:
- carbon monoxide48%1,177 days
- fine particles (PM2.5)28%685 days
- nitrogen dioxide25%608 days
Caguas by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 243 | 226 | 17 | 0 | 0 | 5 | 71 |
| 2024 | 357 | 343 | 13 | 1 | 1 | 3 | 174 |
| 2023 | 256 | 242 | 13 | 1 | 0 | 6 | 105 |
| 2022 | 307 | 291 | 16 | 0 | 0 | 9 | 76 |
| 2021 | 197 | 180 | 17 | 0 | 0 | 14 | 75 |
| 2020 | 318 | 306 | 12 | 0 | 0 | 10 | 72 |
| 2019 | 354 | 322 | 28 | 4 | 0 | 10 | 114 |
| 2018 | 201 | 199 | 2 | 0 | 0 | 9 | 54 |
| 2017 | 226 | 209 | 16 | 1 | 0 | 24 | 101 |
| 2016 | 11 | 9 | 1 | 1 | 0 | 25 | 112 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.