Bad Air Days in Howard County, Maryland: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 855 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (100% particle days).

Which months to watch

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

What to buy, and what not to

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 Howard

The worst recent year was 2023, with 4 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-08	188	PM2.5
2023-06-29	174	PM2.5
2023-06-07	158	PM2.5
2023-06-30	113	PM2.5
2023-06-28	98	PM2.5

Most days, not the worst ones

Across 3,651 monitored days from 2016 to 2025, the air in Howard County rated Good on 72% of them, close to the 72% typical of monitored counties, and Moderate on 28%. The median day sat at AQI 39; one day in ten went above 57.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)80%2,918 days
nitrogen dioxide20%717 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	293	72	0	0	33	78
2024	366	307	59	0	0	32	75
2023	365	268	93	4	3	38	188
2022	365	290	75	0	0	37	70
2021	365	284	81	0	0	36	83
2020	364	297	67	0	0	37	71
2019	365	267	98	0	0	39	81
2018	365	205	160	0	0	47	78
2017	365	234	131	0	0	42	76
2016	366	194	172	0	0	48	87
2015	365	231	134	0	0	41	93
2014	275	76	199	0	0	55	82

*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.