Air quality comparison · Puerto Rico, 16.8 mi (27 km) apart
Caguas vs San Juan Air quality index (AQI) today
Caguas and San Juan are level right now: both read AQI 56 (Moderate).
Over the past 7 days, on modeled daily averages, San Juan averaged AQI 31 against 32, and it was the cleaner of the two on 1 of those days. Caguas has lost more forest since 2001. Caguas has more tree cover.
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Caguas56San Juan56
Head to head
Caguas vs San Juan at a glance
Caguas and San Juan are level, each ahead on 2 of 6 measures. The better figure in each row is marked.
| Caguas | San Juan | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 56 | 56 |
| PM2.5Fine particles, µg/m³. | 12 | 12 |
| Past week's averageUS AQI, 7 days. | 32 | 31 (better) |
| Forest lost since 2001Within 10 km of the center. | 4,010 acres (1,620 ha) | 596 acres (241 ha) (better) |
| Tree coverWithin 1.2 mi (2 km) of the center. | 29.0% (better) | 8.6% |
| Trees still neededTo reach a healthy canopy. | 3.1K (better) | 19.2K |
Air quality today
What is the air like in Caguas and San Juan right now?
Caguas and San Juan are level right now: both read AQI 56 (Moderate). PM2.5 is setting the index in both.
Both readings come from ground stations, and the closest one is the same for both (Cataño 40), so read a small gap with care.
CaguasSan Juan
Concentrations at the same moment as the index above, for the pollutants both places report. Lower is better. The dark marks on the PM2.5 and PM10 rows show the WHO's 24-hour guidelines (15 and 45 µg/m³).
The past week
Which had cleaner air over the past 7 days?
Over the past 7 days, on modeled daily averages, San Juan averaged AQI 31 against 32, and it was the cleaner of the two on 1 of those days. The two are close enough that the air model behind these daily figures barely separates them, so their lines nearly overlap.
- Cleaner days
- Caguas0San Juan1
- Average AQI
- Caguas32San Juan31
- Worst day, AQI
- Caguas55San Juan55
The daily numbers (7 days)
| Day | Caguas | San Juan |
|---|---|---|
| Nov 4 | 55 | 55 |
| Nov 5 | 54 | 54 |
| Nov 6 | 40 | 40 |
| Nov 7 | 12 | 12 |
| Nov 8 | 22 | 22 |
| Nov 9 | 18 | 18 |
| Nov 10 | 21 | 18 |
Daily averages from the CAMS atmospheric model for both places, so the week compares like with like. They can differ from today's reading at the top of the page wherever that comes from a ground station.
What it means today
Is it safe to go outside in Caguas and San Juan today?
Unusually sensitive people should consider limiting long outdoor exertion. Both are in the same EPA band today (Moderate), so the advice is the same.
Exercise outdoors
Fine for most people; unusually sensitive people should take long or hard exercise easier.
Windows
Fine to open; close them if you are sensitive to pollution.
Masks
Not needed for most people.
Air purifier
Worth running if you are sensitive.
Against everywhere else
How do Caguas and San Juan compare with the rest of the world?
Right now Caguas's air is cleaner than 52% of the 5,420 places Airleaf tracks, and San Juan's is cleaner than 52%. Within Puerto Rico, that is 33% and 33% of its 7 measured places.
Cleaner air than…
- Caguas
- Beats 52%
- San Juan
- Beats 52%
More tree cover than…
- Caguas
- Beats 67%
- San Juan
- Beats 18%
Includes model estimates as well as station readings, so it can differ from our most polluted and cleanest air rankings, which use station readings only.
Deforestation · 2001–2025
Which has lost more forest, Caguas or San Juan?
Caguas has lost more: about 4,010 acres (1,620 ha) of forest within 10 km of its center from 2001 to 2025, against 596 acres (241 ha) around San Juan. 3,780 acres (1,530 ha) of that was cleared for good, for farms, mines or towns.
Measured within 10 km of each center, from the yearly satellite maps of forest loss: a wider circle than the one for tree cover, because forest is usually lost at a city's edges.
Worst year: 2017, with 1,830 acres (739 ha) lost.
Worst year: 2017, with 437 acres (177 ha) lost.
| Caguas | San Juan | |
|---|---|---|
| Forest lost since 2001Cleared, burned or logged. | 4,010 acres (1,620 ha) | 596 acres (241 ha) (better) |
| Share of its forestOf what it had in 2000. | 9% (better) | 17% |
| Cleared for goodTurned into farms, mines or towns. | 3,780 acres (1,530 ha) | 201 acres (81 ha) (better) |
| Recent trend2021–2025 against the five years before. | Slowing down | Too little to call |
| Main known cause | Towns and roads (82%) | Storms, floods and other natural causes (64%) |
Satellite timelapses
Watch both change, year by year
A clear satellite photo a year of the land around each city. Press play, turn on the forest cleared since the first year, or drag the before and after.
Caguas
2020: satellite photo from February 2020 of a 5 × 5 km area about 7 km northwest of the city center.
San Juan
2017: satellite photo from February 2017 of a 5 × 5 km area about 7 km southeast of the city center.
Trees
Which has more trees, Caguas or San Juan?
Caguas has more tree cover: 29.0% of the land within 1.2 mi (2 km) of its center against 8.6% around San Juan, or about 91,106 trees against 7,727.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Caguas | San Juan | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 91.1K (better) | 7.7K |
| Trees still neededTo reach the target. Fewer is better. | 3.1K (better) | 19.2K |
| CO₂ absorbed each yearBy the trees already standing. | 2.0M kg (better) | 170K kg |
Tree cover on the satellite image
The same 1.2 mi (2 km) radius around each center, with the tree cover the satellite found marked on it.
Reading these numbers
How this comparison is made
Air quality index
The US EPA index, computed from current pollutant concentrations: ground stations where a place has them nearby, and the CAMS atmospheric model everywhere else. It moves hour to hour, so it is a snapshot rather than a verdict on either place. The guideline marks are from the WHO's 2021 air quality guidelines.
Trees and forest
Tree cover is the share of ground under canopy within 1.2 mi (2 km) of each center, read from Sentinel-2 satellite imagery at 10 m detail. It measures that circle, not the whole municipality, which is what makes the two comparable. Forest loss comes from the University of Maryland's Global Forest Change maps.
More on the method on the About Airleaf page.
Frequently asked
Caguas vs San Juan: your questions answered
Is Caguas cleaner than San Juan?
On air quality they are level right now: both read 56 on the US EPA index. Air quality changes through the day, so this can separate within hours. Over the past 7 days, on modeled daily averages, San Juan averaged AQI 31 against 32, and it was the cleaner of the two on 1 of those days.
Is it safe to exercise outdoors in Caguas and San Juan today?
The advice is the same for both today. Unusually sensitive people should consider limiting long outdoor exertion. Caguas reads AQI 56 and San Juan reads AQI 56.
Which has lost more forest, Caguas or San Juan?
Caguas has lost more: about 4,010 acres (1,620 ha) of forest within 10 km of its center from 2001 to 2025, against 596 acres (241 ha) around San Juan. 3,780 acres (1,530 ha) of that was cleared for good, for farms, mines or towns.
Which has more trees, Caguas or San Juan?
Caguas has more tree cover: 29.0% of the land within 1.2 mi (2 km) of its center against 8.6% around San Juan, or about 91,106 trees against 7,727. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Caguas and San Juan need?
Caguas needs about 3,142 more to reach its canopy target of 30%, and San Juan about 19,228 to reach 30%. The target starts at 30% of the land and rises where air quality is poor.
Why can two places 16.8 mi (27 km) apart read differently?
Air changes over short distances with traffic, industry, wind and hills, and each reading comes from the nearest ground stations or, where there are none, from a regional model. A gap of a few points between neighbors is within normal variation, while a gap that crosses an EPA band is worth noticing.
Are Caguas and San Juan measured the same way?
The method is the same: the US EPA index for air, and Sentinel-2 satellite imagery at 10 m detail over an identical radius for trees. Both readings come from ground stations, and the closest one is the same for both (Cataño 40), so read a small gap with care. Nothing is adjusted for population, city limits or climate.
How often does the Caguas vs San Juan comparison update?
The air readings refresh about once an hour, and each reading's local time is shown at the top of the page. Tree cover comes from the latest clear satellite image of each area (Sep 18, 2026 and Sep 18, 2026), and the forest figures are published yearly.
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