Park County, Wyoming air quality history

Daily Air Quality Index summaries from EPA monitors in Park, Wyoming, 1988–2025.

98%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

355

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Park, Wyoming on 355 days. 348 of those days (98%) were in the Good range, and the median daily AQI was 13. That median is lower than the typical monitored county in Wyoming (median 41 across 17 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 355 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 97% in 1989–2004 versus 95% in 2023–2025.

Years with fewer than 120 monitored days (2001, 2002, 2003, 2005, 2006, 2007…) 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, 2025

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)	355	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Median AQI	90th pct.	Max AQI	Main pollutant
2025	355	348	7	0	13	28	73	PM2.5
2024	355	322	33	0	13	46	88	PM2.5
2023	360	343	16	1	14	33	122	PM2.5
2022	344	314	30	0	20	47	83	PM2.5
2021	152	129	23	0	14	61	98	PM2.5
2020	122	112	8	2	15	41	113	PM2.5
2019	307	292	15	0	38	47	80	Ozone
2018	212	194	16	2	31	47	136	Ozone
2017	121	106	15	0	18	58	87	PM2.5
2016	121	115	6	0	16	32	87	PM2.5
2015	126	118	8	0	18	44	84	PM2.5
2014	122	113	9	0	16	43	59	PM2.5
2013	124	118	6	0	20	42	63	PM2.5
2012	123	106	17	0	21	56	93	PM2.5
2011	122	113	9	0	21	41	79	PM2.5
2010	121	113	8	0	21	41	58	PM2.5
2009	122	118	4	0	23	41	62	PM2.5
2008	120	106	13	1	18	52	118	PM2.5
2007	99	94	5	0	13	34	72	PM2.5
2006	115	114	1	0	10	27	57	PM2.5
2005	115	115	0	0	10	24	41	PM2.5
2004	121	120	1	0	11	25	51	PM2.5
2003	109	106	3	0	14	37	55	PM2.5
2002	112	112	0	0	14	26	44	PM2.5
2001	106	105	1	0	12	29	56	PM2.5
2000	110	103	7	0	15	36	86	PM2.5
1999	50	50	0	0	10	25	38	PM10
1998	53	52	1	0	11	21	52	PM10
1997	44	43	1	0	13	19	55	PM10
1996	49	49	0	0	11	19	29	PM10
1995	57	57	0	0	11	24	37	PM10
1994	58	56	1	1	14	31	109	PM10
1993	107	107	0	0	12	23	50	PM10
1992	119	119	0	0	14	25	47	PM10
1991	117	115	2	0	20	32	80	PM10
1990	160	155	5	0	16	31	70	PM10
1989	156	148	7	1	17	33	131	PM10
1988	51	39	12	0	28	61	98	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.

Counties in Wyoming with a similar median AQI in 2025

All monitored counties in Wyoming

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem