Bad Air Days in San Juan, Puerto Rico: 0 a Year

0 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 996 of 996 monitored counties, where 1 is worst.

Is a purifier worth it 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 worst days on file

In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, 0. Not much has changed.

Date	AQI	Main pollutant
2016-10-25	83	CO
2020-05-21	39	CO
2020-05-22	39	CO
2020-05-20	38	CO
2020-05-24	38	CO

An ordinary day in San Juan

Across 1,108 monitored days from 2016 to 2021, the air in San Juan rated Good on 100% of them, more often than the 72% typical of monitored counties, and Moderate on 0%. The median day sat at AQI 12; one day in ten went above 20.

The pollutant setting the AQI on an ordinary day here:

carbon monoxide100%1,108 days

Year by year

Year	Days monitored	Good	Moderate	Median AQI	Highest AQI
2021	41	41	0	7	10
2020	216	216	0	9	39
2019	277	277	0	14	35
2017	246	246	0	8	35
2016	328	327	1	15	83
2015	329	321	8	13	66
2014	358	358	0	17	31
2013	348	348	0	16	32
2012	299	281	18	18	74
2011	295	282	13	19	69
2010	253	253	0	17	28

Elsewhere in Puerto Rico

Catano11/yr
Juncos5/yr
Bayamon3/yr
Mayagnez3/yr
Ponce2/yr
Guaynabo2/yr
Caguas1/yr
Fajardothin data

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.