Bad Air Days in Franklin County, Pennsylvania: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 908 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (0% particle days).

When the bad days come in Franklin

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

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 34 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2023, with 2 bad days on 301 monitored days.

Date	AQI	Main pollutant
2023-06-29	133	Ozone
2023-06-01	126	Ozone
2023-04-21	97	Ozone
2023-05-12	90	Ozone
2023-06-03	90	Ozone

Most days, not the worst ones

Across 3,200 monitored days from 2016 to 2025, the air in Franklin County rated Good on 95% of them, more often than the 72% typical of monitored counties, and Moderate on 5%. The median day sat at AQI 35; one day in ten went above 46.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,200 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Median AQI	Highest AQI
2025*	295	270	25	0	37	87
2024	327	305	22	0	35	90
2023	301	267	32	2	39	133
2022	237	225	12	0	39	84
2021	288	274	14	0	35	77
2020	363	363	0	0	32	50
2019	341	324	17	0	36	80
2018	353	343	10	0	32	74
2017	358	354	4	0	33	67
2016	337	325	12	0	33	74
2015	359	340	19	0	34	77
2014	337	311	26	0	38	87
2013	344	279	61	4	40	115
2012	273	213	59	1	40	115
2011	180	150	29	1	41	112
2010	210	150	58	2	45	122

*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, and on why a purifier does not touch ozone in smoke vs ozone.