EnviroNearby

Platte County, Wyoming air quality history

Daily Air Quality Index summaries from EPA monitors in Platte, Wyoming, 1995–2025.

91%
Good days in 2025
15
Median daily AQI, 2025
12
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Platte, Wyoming on 361 days. 327 of those days (91%) were in the Good range, and the median daily AQI was 15. 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 coarse particles (PM10) on 361 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 89% in 2020–2022 versus 90% in 2023–2025.

Years with fewer than 120 monitored days (2014, 2015, 2016, 2017, 2018, 2019…) 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.

Share of monitored days in each AQI category, by year0%25%50%75%100%1995: Good 57 of 59 days1995: Moderate 2 of 59 days19951996: Good 38 of 40 days1996: Moderate 2 of 40 days1997: Good 46 of 46 days1998: Good 59 of 61 days1998: Moderate 2 of 61 days1999: Good 60 of 60 days2000: Good 59 of 61 days2000: Moderate 2 of 61 days20002001: Good 59 of 60 days2001: Moderate 1 of 60 days2002: Good 55 of 61 days2002: Moderate 6 of 61 days2003: Good 55 of 58 days2003: Moderate 3 of 58 days2004: Good 55 of 58 days2004: Moderate 3 of 58 days2005: Good 43 of 44 days2005: Moderate 1 of 44 days20052006: Good 57 of 61 days2006: Moderate 4 of 61 days2007: Good 40 of 42 days2007: Moderate 1 of 42 days2007: Unhealthy for Sensitive Groups 1 of 42 days2008: Good 55 of 59 days2008: Moderate 4 of 59 days2009: Good 57 of 61 days2009: Moderate 4 of 61 days2010: Good 59 of 61 days2010: Moderate 2 of 61 days20102011: Good 58 of 61 days2011: Moderate 3 of 61 days2012: Good 57 of 61 days2012: Moderate 4 of 61 days2013: Good 56 of 58 days2013: Moderate 2 of 58 days2014: Good 58 of 60 days2014: Moderate 2 of 60 days2015: Good 57 of 60 days2015: Moderate 3 of 60 days20152016: Good 50 of 57 days2016: Moderate 7 of 57 days2017: Good 54 of 60 days2017: Moderate 6 of 60 days2018: Good 58 of 61 days2018: Moderate 3 of 61 days2019: Good 56 of 60 days2019: Moderate 3 of 60 days2019: Unhealthy for Sensitive Groups 1 of 60 days2020: Good 202 of 224 days2020: Moderate 20 of 224 days2020: Unhealthy for Sensitive Groups 1 of 224 days2020: Very Unhealthy 1 of 224 days20202021: Good 324 of 362 days2021: Moderate 28 of 362 days2021: Unhealthy for Sensitive Groups 2 of 362 days2021: Unhealthy 3 of 362 days2021: Very Unhealthy 1 of 362 days2021: Hazardous 4 of 362 days2022: Good 311 of 355 days2022: Moderate 29 of 355 days2022: Unhealthy for Sensitive Groups 8 of 355 days2022: Unhealthy 3 of 355 days2022: Hazardous 4 of 355 days2023: Good 334 of 364 days2023: Moderate 25 of 364 days2023: Unhealthy for Sensitive Groups 1 of 364 days2023: Unhealthy 3 of 364 days2023: Hazardous 1 of 364 days2024: Good 325 of 366 days2024: Moderate 32 of 366 days2024: Unhealthy for Sensitive Groups 6 of 366 days2024: Unhealthy 1 of 366 days2024: Hazardous 2 of 366 days2025: Good 327 of 361 days2025: Moderate 22 of 361 days2025: Unhealthy for Sensitive Groups 3 of 361 days2025: Unhealthy 3 of 361 days2025: Very Unhealthy 2 of 361 days2025: Hazardous 4 of 361 days2025
  • 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 and 90th-percentile daily AQI, by year0501001995: 90th percentile AQI 281996: 90th percentile AQI 281997: 90th percentile AQI 311998: 90th percentile AQI 321999: 90th percentile AQI 302000: 90th percentile AQI 312001: 90th percentile AQI 312002: 90th percentile AQI 462003: 90th percentile AQI 392004: 90th percentile AQI 362005: 90th percentile AQI 312006: 90th percentile AQI 402007: 90th percentile AQI 322008: 90th percentile AQI 492009: 90th percentile AQI 412010: 90th percentile AQI 282011: 90th percentile AQI 292012: 90th percentile AQI 372013: 90th percentile AQI 352014: 90th percentile AQI 352015: 90th percentile AQI 462016: 90th percentile AQI 522017: 90th percentile AQI 572018: 90th percentile AQI 362019: 90th percentile AQI 372020: 90th percentile AQI 502021: 90th percentile AQI 512022: 90th percentile AQI 542023: 90th percentile AQI 472024: 90th percentile AQI 532025: 90th percentile AQI 471995: Median AQI 101996: Median AQI 111997: Median AQI 171998: Median AQI 151999: Median AQI 132000: Median AQI 142001: Median AQI 182002: Median AQI 192003: Median AQI 142004: Median AQI 142005: Median AQI 152006: Median AQI 192007: Median AQI 162008: Median AQI 182009: Median AQI 152010: Median AQI 122011: Median AQI 162012: Median AQI 172013: Median AQI 142014: Median AQI 172015: Median AQI 142016: Median AQI 162017: Median AQI 152018: Median AQI 152019: Median AQI 142020: Median AQI 192021: Median AQI 162022: Median AQI 172023: Median AQI 142024: Median AQI 192025: Median AQI 151995200020052010201520202025
  • 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.

PollutantDays as main pollutantShare of monitored days
Coarse particles (PM10)361100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253613272233241547723PM10
20243663253261021953927PM10
20233643342513011447320PM10
20223553112983041754692PM10
20213623242823141651682PM10
20202242022010101950283PM10
20196056310001437108PM10
2018615830000153655PM10
2017605460000155772PM10
2016575070000165266PM10
2015605730000144686PM10
2014605820000173588PM10
2013585620000143559PM10
2012615740000173786PM10
2011615830000162958PM10
2010615920000122859PM10
2009615740000154156PM10
2008595540000184968PM10
20074240110001632120PM10
2006615740000194091PM10
2005444310000153166PM10
2004585530000143687PM10
2003585530000143969PM10
2002615560000194662PM10
2001605910000183162PM10
2000615920000143181PM10
1999606000000133042PM10
1998615920000153270PM10
1997464600000173149PM10
1996403820000112864PM10
1995595720000102861PM10

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 1995–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem