Bad Air Days in Hanover County, Virginia: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 827 of 996 monitored counties, where 1 is worst.

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

Which months to watch

Most bad days here fall in April and May. 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 Hanover

In 2000 to 2009 this county averaged 36 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2016, with 2 bad days on 207 monitored days.

Date	AQI	Main pollutant
2016-04-19	105	Ozone
2016-05-26	105	Ozone
2023-04-13	101	Ozone
2018-06-30	97	Ozone
2023-04-20	97	Ozone

Most days, not the worst ones

Across 2,370 monitored days from 2016 to 2025, the air in Hanover County rated Good on 92% of them, more often than the 72% typical of monitored counties, and Moderate on 8%. The median day sat at AQI 38; one day in ten went above 50.

The pollutant setting the AQI on an ordinary day here:

ozone100%2,370 days

Hanover County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	241	233	8	0	0	36	77
2024	245	228	17	0	0	39	74
2023	229	213	15	1	0	40	101
2022	239	226	13	0	0	39	77
2021	245	228	17	0	0	38	87
2020	245	243	2	0	0	34	64
2019	243	216	27	0	0	41	90
2018	238	209	29	0	0	40	97
2017	238	215	23	0	0	39	87
2016	207	174	31	2	0	39	105
2015	214	189	25	0	0	40	74
2014	200	175	25	0	0	42	93
2013	196	172	23	1	0	39	140
2012	208	160	43	5	2	43	169
2011	206	149	47	10	0	44	133
2010	213	115	84	14	1	49	154

*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.