Winona County, Minnesota air quality history

Daily Air Quality Index summaries from EPA monitors in Winona, Minnesota, 1998–2025.

93%

Good days in 2024

Median daily AQI, 2024

Days above 100 in 2024

122

Days with an AQI in 2024 (of 366)

In 2024, EPA reported a daily Air Quality Index (AQI) for Winona, Minnesota on 122 days. 114 of those days (93%) were in the Good range, and the median daily AQI was 20. That median is lower than the typical monitored county in Minnesota (median 38 across 21 counties), and lower than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 122 days. Across the years with fuller monitoring, the share of Good days rose: an average of 75% in 2008–2012 versus 92% in 2015–2024.

EPA did not report an AQI for every day of 2024 here (122 of 366 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2018, 2019, 2020, 2021, 2023, 2025…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2024

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	122	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	99	83	16	0	0	21	55	89	PM2.5
2024	122	114	8	0	0	20	41	63	PM2.5
2023	119	95	22	1	1	28	58	169	PM2.5
2022	121	113	8	0	0	22	44	65	PM2.5
2021	116	101	15	0	0	24	52	80	PM2.5
2020	119	112	7	0	0	22	40	57	PM2.5
2019	115	102	13	0	0	21	52	65	PM2.5
2018	113	96	17	0	0	26	54	80	PM2.5
2017	119	104	15	0	0	22	52	65	PM2.5
2016	117	106	11	0	0	19	46	72	PM2.5
2015	120	108	12	0	0	24	52	76	PM2.5
2014	356	250	105	1	0	40	62	110	PM2.5
2013	120	101	19	0	0	29	54	62	PM2.5
2012	120	102	18	0	0	27	56	86	PM2.5
2011	120	88	32	0	0	29	59	73	PM2.5
2010	118	89	29	0	0	31	56	94	PM2.5
2009	113	89	24	0	0	29	65	91	PM2.5
2008	120	80	40	0	0	39	62	97	PM2.5
2007	116	86	29	1	0	36	61	116	PM2.5
2006	114	86	28	0	0	33	57	82	PM2.5
2005	119	76	40	2	1	36	67	152	PM2.5
2004	115	79	35	1	0	31	65	111	PM2.5
2003	113	71	42	0	0	39	70	92	PM2.5
2002	49	28	21	0	0	44	69	81	PM2.5
1999	37	37	0	0	0	14	22	39	PM10
1998	10	10	0	0	0	12	27	27	PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

All monitored counties in Minnesota

Source: U.S. EPA AirData, “Annual AQI by County” files for 1998–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem