Bad Air Days in Baltimore City, Maryland: 4 a Year

4 bad air days a year

About the middle of monitored US counties. Ranked 276 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (18% particle days).

When the bad days come in Baltimore (City)

Most bad days here fall in July and June and May. Averaged over 2016 to 2025.

Is a purifier worth it here?

Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.

The record for Baltimore (City)

In 2000 to 2009 this county averaged 18 bad days a year; in 2016 to 2025, 4. The air has improved. The worst recent year was 2018, with 8 bad days on 364 monitored days.

Date	AQI	Main pollutant
2023-06-08	192	PM2.5
2023-06-29	179	PM2.5
2023-06-07	170	PM2.5
2016-07-27	156	Ozone
2025-07-29	136	Ozone

Most days, not the worst ones

Across 3,632 monitored days from 2016 to 2025, the air in Baltimore City rated Good on 64% of them, less often than the 72% typical of monitored counties, and Moderate on 35%. The median day sat at AQI 45; one day in ten went above 66.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)55%2,001 days
ozone39%1,401 days
nitrogen dioxide6%229 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	248	114	2	0	43	136
2024	365	258	101	6	0	42	112
2023	365	242	116	7	3	44	192
2022	353	242	109	2	0	44	112
2021	364	243	121	0	0	43	93
2020	363	293	70	0	0	38	97
2019	363	217	140	6	0	46	126
2018	364	182	174	8	0	51	129
2017	365	221	141	3	0	46	112
2016	366	192	168	6	1	49	156
2015	365	159	200	6	0	53	140
2014	365	146	219	0	0	52	95
2013	365	150	214	1	0	52	108
2012	366	126	235	5	1	55	154
2011	365	111	240	14	1	56	154
2010	365	129	225	11	1	55	187

*2025 may be a partial year in EPA's file.

Elsewhere in Maryland

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.