Bad Air Days in Pierce County, Washington: 5 a Year

5 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 203 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (98% particle days).

When the bad days come in Pierce

Most bad days here fall in August and September. Averaged over 2016 to 2025.

What to buy, and what not to

Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.

Better or worse than it was

In 2000 to 2009 this county averaged 17 bad days a year; in 2016 to 2025, 5. The air has improved. The worst recent year was 2017, with 13 bad days on 365 monitored days.

Date	AQI	Main pollutant
2020-09-12	256	PM2.5
2020-09-14	256	PM2.5
2020-09-13	244	PM2.5
2020-09-15	234	PM2.5
2020-09-11	199	PM2.5

Most days, not the worst ones

Across 3,653 monitored days from 2016 to 2025, the air in Pierce County rated Good on 70% of them, close to the 72% typical of monitored counties, and Moderate on 29%. The median day sat at AQI 43; one day in ten went above 65.

The pollutant setting the AQI on an ordinary day here:

ozone51%1,865 days
fine particles (PM2.5)48%1,739 days
nitrogen dioxide1%49 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	267	98	0	0	44	100
2024	366	265	100	1	1	44	166
2023	365	273	89	3	3	42	195
2022	365	239	115	11	2	44	178
2021	365	269	96	0	0	42	94
2020	366	256	99	11	7	42	256
2019	365	234	129	2	0	44	142
2018	365	234	120	11	6	44	188
2017	365	242	110	13	7	45	176
2016	366	269	96	1	1	42	156
2015	365	235	123	7	1	44	166
2014	365	251	112	2	0	42	114
2013	365	217	143	5	0	46	113
2012	366	237	124	5	0	44	144
2011	365	236	119	10	1	44	152
2010	365	246	119	0	0	43	97

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

Elsewhere in Washington

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.