Bad Air Days in Forsyth County, North Carolina: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 506 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (50% particle days).

Which months to watch

Most bad days here fall in June and July. 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.

The record for Forsyth

In 2000 to 2009 this county averaged 29 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 7 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-29	154	PM2.5
2023-07-17	147	PM2.5
2022-02-02	137	PM2.5
2023-07-18	131	PM2.5
2021-11-30	124	PM2.5

An ordinary day in Forsyth

Across 3,653 monitored days from 2016 to 2025, the air in Forsyth County rated Good on 56% of them, less often than the 72% typical of monitored counties, and Moderate on 43%. The median day sat at AQI 48; one day in ten went above 65.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)63%2,296 days
ozone36%1,325 days
nitrogen dioxide1%32 days

Forsyth County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	232	133	0	0	45	100
2024	366	210	152	4	0	47	122
2023	365	165	193	7	1	52	154
2022	365	209	155	1	0	48	137
2021	365	201	161	3	0	48	124
2020	366	233	133	0	0	45	97
2019	365	175	190	0	0	51	97
2018	365	189	174	2	0	50	101
2017	365	223	142	0	0	47	100
2016	366	218	145	3	0	47	119
2015	365	193	169	3	0	49	126
2014	365	154	211	0	0	52	100
2013	365	180	183	2	0	51	122
2012	366	163	191	12	2	52	154
2011	365	142	210	13	0	54	147
2010	365	105	237	23	3	58	169

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