Bad Air Days in Centre County, Pennsylvania: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 607 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (64% particle days).

Which months to watch

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

What actually helps 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.

Better or worse than it was

In 2000 to 2009 this county averaged 20 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2023, with 8 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-07	199	PM2.5
2023-06-29	181	PM2.5
2023-06-08	165	PM2.5
2023-06-30	160	PM2.5
2023-06-28	157	PM2.5

An ordinary day in Centre

Across 3,653 monitored days from 2016 to 2025, the air in Centre County rated Good on 65% of them, less often than the 72% typical of monitored counties, and Moderate on 34%. The median day sat at AQI 44; one day in ten went above 62.

The pollutant setting the AQI on an ordinary day here:

ozone52%1,888 days
fine particles (PM2.5)48%1,762 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	271	93	1	0	41	101
2024	366	287	79	0	0	40	97
2023	365	239	118	8	5	45	199
2022	365	240	125	0	0	44	89
2021	365	241	123	1	0	43	114
2020	366	287	79	0	0	41	91
2019	365	192	173	0	0	49	99
2018	365	225	138	2	0	44	122
2017	365	174	191	0	0	51	100
2016	366	232	132	2	0	45	122
2015	365	204	159	2	0	46	108
2014	365	177	188	0	0	51	90
2013	365	210	153	2	0	47	112
2012	366	140	217	9	1	54	154
2011	365	183	173	9	0	50	143
2010	365	187	170	8	0	50	133

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

Elsewhere in Pennsylvania

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.