EnviroNearby

Washoe County, Nevada air quality history

Daily Air Quality Index summaries from EPA monitors in Washoe, Nevada, 1980–2025.

50%
Good days in 2025
50
Median daily AQI, 2025
2
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Washoe, Nevada on 365 days. 183 of those days (50%) were in the Good range, and the median daily AQI was 50. That median is higher than the typical monitored county in Nevada (median 42 across 9 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 261 days. Across the years with fuller monitoring, the share of Good days rose: an average of 42% in 1980–1982 versus 51% in 2023–2025.

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%1980: Good 165 of 366 days1980: Moderate 125 of 366 days1980: Unhealthy for Sensitive Groups 62 of 366 days1980: Unhealthy 11 of 366 days1980: Very Unhealthy 3 of 366 days19801981: Good 93 of 362 days1981: Moderate 192 of 362 days1981: Unhealthy for Sensitive Groups 71 of 362 days1981: Unhealthy 6 of 362 days1982: Good 196 of 364 days1982: Moderate 128 of 364 days1982: Unhealthy for Sensitive Groups 31 of 364 days1982: Unhealthy 5 of 364 days1982: Very Unhealthy 4 of 364 days1983: Good 244 of 365 days1983: Moderate 106 of 365 days1983: Unhealthy for Sensitive Groups 5 of 365 days1983: Unhealthy 7 of 365 days1983: Very Unhealthy 3 of 365 days1984: Good 109 of 366 days1984: Moderate 185 of 366 days1984: Unhealthy for Sensitive Groups 65 of 366 days1984: Unhealthy 5 of 366 days1984: Very Unhealthy 2 of 366 days1985: Good 146 of 365 days1985: Moderate 189 of 365 days1985: Unhealthy for Sensitive Groups 25 of 365 days1985: Unhealthy 4 of 365 days1985: Very Unhealthy 1 of 365 days19851986: Good 92 of 365 days1986: Moderate 184 of 365 days1986: Unhealthy for Sensitive Groups 78 of 365 days1986: Unhealthy 10 of 365 days1986: Very Unhealthy 1 of 365 days1987: Good 201 of 365 days1987: Moderate 142 of 365 days1987: Unhealthy for Sensitive Groups 22 of 365 days1988: Good 188 of 366 days1988: Moderate 146 of 366 days1988: Unhealthy for Sensitive Groups 30 of 366 days1988: Unhealthy 2 of 366 days1989: Good 197 of 357 days1989: Moderate 141 of 357 days1989: Unhealthy for Sensitive Groups 18 of 357 days1989: Unhealthy 1 of 357 days1990: Good 144 of 365 days1990: Moderate 193 of 365 days1990: Unhealthy for Sensitive Groups 22 of 365 days1990: Unhealthy 4 of 365 days1990: Very Unhealthy 2 of 365 days19901991: Good 169 of 365 days1991: Moderate 178 of 365 days1991: Unhealthy for Sensitive Groups 18 of 365 days1992: Good 195 of 365 days1992: Moderate 159 of 365 days1992: Unhealthy for Sensitive Groups 11 of 365 days1993: Good 219 of 365 days1993: Moderate 141 of 365 days1993: Unhealthy for Sensitive Groups 5 of 365 days1994: Good 204 of 365 days1994: Moderate 155 of 365 days1994: Unhealthy for Sensitive Groups 6 of 365 days1995: Good 241 of 365 days1995: Moderate 117 of 365 days1995: Unhealthy for Sensitive Groups 7 of 365 days19951996: Good 218 of 366 days1996: Moderate 134 of 366 days1996: Unhealthy for Sensitive Groups 14 of 366 days1997: Good 267 of 365 days1997: Moderate 95 of 365 days1997: Unhealthy for Sensitive Groups 3 of 365 days1998: Good 251 of 365 days1998: Moderate 107 of 365 days1998: Unhealthy for Sensitive Groups 7 of 365 days1999: Good 196 of 365 days1999: Moderate 158 of 365 days1999: Unhealthy for Sensitive Groups 9 of 365 days1999: Unhealthy 2 of 365 days2000: Good 221 of 366 days2000: Moderate 142 of 366 days2000: Unhealthy for Sensitive Groups 3 of 366 days20002001: Good 213 of 365 days2001: Moderate 136 of 365 days2001: Unhealthy for Sensitive Groups 15 of 365 days2001: Unhealthy 1 of 365 days2002: Good 218 of 365 days2002: Moderate 134 of 365 days2002: Unhealthy for Sensitive Groups 13 of 365 days2003: Good 241 of 365 days2003: Moderate 115 of 365 days2003: Unhealthy for Sensitive Groups 8 of 365 days2003: Unhealthy 1 of 365 days2004: Good 237 of 366 days2004: Moderate 123 of 366 days2004: Unhealthy for Sensitive Groups 6 of 366 days2005: Good 163 of 365 days2005: Moderate 194 of 365 days2005: Unhealthy for Sensitive Groups 7 of 365 days2005: Unhealthy 1 of 365 days20052006: Good 210 of 365 days2006: Moderate 140 of 365 days2006: Unhealthy for Sensitive Groups 15 of 365 days2007: Good 210 of 365 days2007: Moderate 144 of 365 days2007: Unhealthy for Sensitive Groups 11 of 365 days2008: Good 218 of 366 days2008: Moderate 133 of 366 days2008: Unhealthy for Sensitive Groups 12 of 366 days2008: Unhealthy 3 of 366 days2009: Good 227 of 365 days2009: Moderate 134 of 365 days2009: Unhealthy for Sensitive Groups 4 of 365 days2010: Good 221 of 365 days2010: Moderate 140 of 365 days2010: Unhealthy for Sensitive Groups 4 of 365 days20102011: Good 197 of 365 days2011: Moderate 164 of 365 days2011: Unhealthy for Sensitive Groups 4 of 365 days2012: Good 124 of 366 days2012: Moderate 222 of 366 days2012: Unhealthy for Sensitive Groups 12 of 366 days2012: Hazardous 8 of 366 days2013: Good 121 of 365 days2013: Moderate 209 of 365 days2013: Unhealthy for Sensitive Groups 17 of 365 days2013: Unhealthy 4 of 365 days2013: Hazardous 14 of 365 days2014: Good 143 of 365 days2014: Moderate 207 of 365 days2014: Unhealthy for Sensitive Groups 7 of 365 days2014: Unhealthy 3 of 365 days2014: Hazardous 5 of 365 days2015: Good 165 of 365 days2015: Moderate 188 of 365 days2015: Unhealthy for Sensitive Groups 12 of 365 days20152016: Good 203 of 366 days2016: Moderate 156 of 366 days2016: Unhealthy for Sensitive Groups 7 of 366 days2017: Good 165 of 365 days2017: Moderate 196 of 365 days2017: Unhealthy for Sensitive Groups 4 of 365 days2018: Good 177 of 365 days2018: Moderate 169 of 365 days2018: Unhealthy for Sensitive Groups 19 of 365 days2019: Good 214 of 365 days2019: Moderate 151 of 365 days2020: Good 193 of 366 days2020: Moderate 149 of 366 days2020: Unhealthy for Sensitive Groups 11 of 366 days2020: Unhealthy 11 of 366 days2020: Very Unhealthy 2 of 366 days20202021: Good 174 of 365 days2021: Moderate 156 of 365 days2021: Unhealthy for Sensitive Groups 16 of 365 days2021: Unhealthy 10 of 365 days2021: Very Unhealthy 8 of 365 days2021: Hazardous 1 of 365 days2022: Good 180 of 365 days2022: Moderate 176 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2022: Unhealthy 4 of 365 days2022: Very Unhealthy 4 of 365 days2023: Good 191 of 365 days2023: Moderate 174 of 365 days2024: Good 188 of 366 days2024: Moderate 174 of 366 days2024: Unhealthy for Sensitive Groups 4 of 366 days2025: Good 183 of 365 days2025: Moderate 180 of 365 days2025: Unhealthy for Sensitive Groups 2 of 365 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 year0501001501980: 90th percentile AQI 1141981: 90th percentile AQI 1081982: 90th percentile AQI 1051983: 90th percentile AQI 741984: 90th percentile AQI 1111985: 90th percentile AQI 1001986: 90th percentile AQI 1221987: 90th percentile AQI 941988: 90th percentile AQI 971989: 90th percentile AQI 901990: 90th percentile AQI 971991: 90th percentile AQI 901992: 90th percentile AQI 841993: 90th percentile AQI 711994: 90th percentile AQI 801995: 90th percentile AQI 671996: 90th percentile AQI 841997: 90th percentile AQI 671998: 90th percentile AQI 771999: 90th percentile AQI 802000: 90th percentile AQI 802001: 90th percentile AQI 802002: 90th percentile AQI 872003: 90th percentile AQI 802004: 90th percentile AQI 742005: 90th percentile AQI 842006: 90th percentile AQI 872007: 90th percentile AQI 802008: 90th percentile AQI 802009: 90th percentile AQI 712010: 90th percentile AQI 802011: 90th percentile AQI 742012: 90th percentile AQI 892013: 90th percentile AQI 992014: 90th percentile AQI 842015: 90th percentile AQI 802016: 90th percentile AQI 772017: 90th percentile AQI 772018: 90th percentile AQI 802019: 90th percentile AQI 642020: 90th percentile AQI 852021: 90th percentile AQI 952022: 90th percentile AQI 742023: 90th percentile AQI 712024: 90th percentile AQI 772025: 90th percentile AQI 711980: Median AQI 571981: Median AQI 771982: Median AQI 481983: Median AQI 441984: Median AQI 671985: Median AQI 571986: Median AQI 681987: Median AQI 471988: Median AQI 501989: Median AQI 481990: Median AQI 541991: Median AQI 511992: Median AQI 501993: Median AQI 471994: Median AQI 491995: Median AQI 471996: Median AQI 471997: Median AQI 441998: Median AQI 451999: Median AQI 492000: Median AQI 472001: Median AQI 482002: Median AQI 482003: Median AQI 462004: Median AQI 462005: Median AQI 532006: Median AQI 472007: Median AQI 482008: Median AQI 482009: Median AQI 472010: Median AQI 472011: Median AQI 492012: Median AQI 582013: Median AQI 572014: Median AQI 542015: Median AQI 522016: Median AQI 492017: Median AQI 522018: Median AQI 512019: Median AQI 482020: Median AQI 502021: Median AQI 512022: Median AQI 512023: Median AQI 502024: Median AQI 502025: Median AQI 501980198519901995200020052010201520202025
  • 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
Ozone26172%
Fine particles (PM2.5)10128%
Coarse particles (PM10)31%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536518318020005071112Ozone
202436618817440005077119Ozone
20233651911740000507197Ozone
202236518017614405174259Ozone
20213651741561610815195333Ozone
20203661931491111205085265Ozone
20193652141510000486497Ozone
2018365177169190005180146Ozone
201736516519640005277126Ozone
201636620315670004977108Ozone
2015365165188120005280115Ozone
201436514320773055484935Ozone
20133651212091740145799939Ozone
2012366124222120085889939Ozone
201136519716440004974136Ozone
201036522114040004780122Ozone
200936522713440004771145Ozone
2008366218133123004880193Ozone
2007365210144110004880115Ozone
2006365210140150004787122Ozone
200536516319471005384157Ozone
200436623712360004674126Ozone
200336524111581004680161Ozone
2002365218134130004887136Ozone
2001365213136151004880182Ozone
200036622114230004780107Ozone
199936519615892004980161Ozone
199836525110770004577133Ozone
19973652679530004467108Ozone
1996366218134140004784140Ozone
199536524111770004767126Ozone
199436520415560004980129Ozone
199336521914150004771122Ozone
1992365195159110005084119Ozone
1991365169178180005190143Ozone
1990365144193224205497206Ozone
1989357197141181004890159CO
1988366188146302005097200Ozone
1987365201142220004794141CO
19863659218478101068122218Ozone
19853651461892541057100255NO2
19843661091856552067111240Ozone
198336524410657304474216Ozone
19823641961283154048105214Ozone
1981362931927160077108193NO2
198036616512562113057114220NO2

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 Nevada with a similar median AQI in 2025

All monitored counties in Nevada

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem