EnviroNearby

Multnomah County, Oregon air quality history

Daily Air Quality Index summaries from EPA monitors in Multnomah, Oregon, 1980–2025.

78%
Good days in 2025
37
Median daily AQI, 2025
0
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 Multnomah, Oregon on 365 days. 283 of those days (78%) were in the Good range, and the median daily AQI was 37. That median is higher than the typical monitored county in Oregon (median 29 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 187 days. Across the years with fuller monitoring, the share of Good days rose: an average of 37% in 1980–1982 versus 79% 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 112 of 366 days1980: Moderate 235 of 366 days1980: Unhealthy for Sensitive Groups 16 of 366 days1980: Unhealthy 2 of 366 days1980: Very Unhealthy 1 of 366 days19801981: Good 125 of 365 days1981: Moderate 216 of 365 days1981: Unhealthy for Sensitive Groups 21 of 365 days1981: Unhealthy 3 of 365 days1982: Good 173 of 365 days1982: Moderate 185 of 365 days1982: Unhealthy for Sensitive Groups 5 of 365 days1982: Unhealthy 2 of 365 days1983: Good 187 of 365 days1983: Moderate 164 of 365 days1983: Unhealthy for Sensitive Groups 12 of 365 days1983: Unhealthy 2 of 365 days1984: Good 176 of 366 days1984: Moderate 187 of 366 days1984: Unhealthy for Sensitive Groups 3 of 366 days1985: Good 224 of 365 days1985: Moderate 139 of 365 days1985: Unhealthy for Sensitive Groups 2 of 365 days19851986: Good 234 of 365 days1986: Moderate 123 of 365 days1986: Unhealthy for Sensitive Groups 8 of 365 days1987: Good 246 of 365 days1987: Moderate 115 of 365 days1987: Unhealthy for Sensitive Groups 4 of 365 days1988: Good 186 of 366 days1988: Moderate 177 of 366 days1988: Unhealthy for Sensitive Groups 3 of 366 days1989: Good 212 of 365 days1989: Moderate 148 of 365 days1989: Unhealthy for Sensitive Groups 5 of 365 days1990: Good 227 of 365 days1990: Moderate 138 of 365 days19901991: Good 258 of 365 days1991: Moderate 103 of 365 days1991: Unhealthy for Sensitive Groups 4 of 365 days1992: Good 290 of 363 days1992: Moderate 73 of 363 days1993: Good 307 of 365 days1993: Moderate 58 of 365 days1994: Good 311 of 365 days1994: Moderate 54 of 365 days1995: Good 333 of 365 days1995: Moderate 32 of 365 days19951996: Good 331 of 363 days1996: Moderate 32 of 363 days1997: Good 349 of 362 days1997: Moderate 13 of 362 days1998: Good 354 of 364 days1998: Moderate 10 of 364 days1999: Good 214 of 365 days1999: Moderate 145 of 365 days1999: Unhealthy for Sensitive Groups 5 of 365 days1999: Unhealthy 1 of 365 days2000: Good 186 of 366 days2000: Moderate 175 of 366 days2000: Unhealthy for Sensitive Groups 3 of 366 days2000: Unhealthy 2 of 366 days20002001: Good 192 of 365 days2001: Moderate 169 of 365 days2001: Unhealthy for Sensitive Groups 3 of 365 days2001: Unhealthy 1 of 365 days2002: Good 232 of 365 days2002: Moderate 130 of 365 days2002: Unhealthy for Sensitive Groups 3 of 365 days2003: Good 306 of 365 days2003: Moderate 59 of 365 days2004: Good 181 of 366 days2004: Moderate 177 of 366 days2004: Unhealthy for Sensitive Groups 6 of 366 days2004: Unhealthy 2 of 366 days2005: Good 208 of 365 days2005: Moderate 152 of 365 days2005: Unhealthy for Sensitive Groups 4 of 365 days2005: Unhealthy 1 of 365 days20052006: Good 243 of 365 days2006: Moderate 115 of 365 days2006: Unhealthy for Sensitive Groups 6 of 365 days2006: Unhealthy 1 of 365 days2007: Good 238 of 365 days2007: Moderate 119 of 365 days2007: Unhealthy for Sensitive Groups 7 of 365 days2007: Unhealthy 1 of 365 days2008: Good 229 of 366 days2008: Moderate 132 of 366 days2008: Unhealthy for Sensitive Groups 5 of 366 days2009: Good 231 of 365 days2009: Moderate 131 of 365 days2009: Unhealthy for Sensitive Groups 3 of 365 days2010: Good 283 of 365 days2010: Moderate 82 of 365 days20102011: Good 260 of 365 days2011: Moderate 99 of 365 days2011: Unhealthy for Sensitive Groups 6 of 365 days2012: Good 263 of 366 days2012: Moderate 102 of 366 days2012: Unhealthy for Sensitive Groups 1 of 366 days2013: Good 245 of 365 days2013: Moderate 115 of 365 days2013: Unhealthy for Sensitive Groups 5 of 365 days2014: Good 290 of 365 days2014: Moderate 74 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 277 of 365 days2015: Moderate 86 of 365 days2015: Unhealthy 2 of 365 days20152016: Good 324 of 366 days2016: Moderate 41 of 366 days2016: Unhealthy for Sensitive Groups 1 of 366 days2017: Good 278 of 365 days2017: Moderate 81 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2017: Unhealthy 5 of 365 days2018: Good 272 of 365 days2018: Moderate 84 of 365 days2018: Unhealthy for Sensitive Groups 8 of 365 days2018: Unhealthy 1 of 365 days2019: Good 283 of 365 days2019: Moderate 82 of 365 days2020: Good 275 of 366 days2020: Moderate 82 of 366 days2020: Unhealthy for Sensitive Groups 1 of 366 days2020: Very Unhealthy 2 of 366 days2020: Hazardous 6 of 366 days20202021: Good 294 of 365 days2021: Moderate 70 of 365 days2021: Unhealthy for Sensitive Groups 1 of 365 days2022: Good 266 of 365 days2022: Moderate 94 of 365 days2022: Unhealthy for Sensitive Groups 3 of 365 days2022: Unhealthy 2 of 365 days2023: Good 267 of 365 days2023: Moderate 97 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days2024: Good 311 of 366 days2024: Moderate 55 of 366 days2025: Good 283 of 365 days2025: Moderate 82 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 year0501001980: 90th percentile AQI 951981: 90th percentile AQI 911982: 90th percentile AQI 741983: 90th percentile AQI 801984: 90th percentile AQI 731985: 90th percentile AQI 691986: 90th percentile AQI 731987: 90th percentile AQI 691988: 90th percentile AQI 741989: 90th percentile AQI 701990: 90th percentile AQI 641991: 90th percentile AQI 731992: 90th percentile AQI 601993: 90th percentile AQI 541994: 90th percentile AQI 541995: 90th percentile AQI 501996: 90th percentile AQI 491997: 90th percentile AQI 451998: 90th percentile AQI 421999: 90th percentile AQI 662000: 90th percentile AQI 742001: 90th percentile AQI 702002: 90th percentile AQI 672003: 90th percentile AQI 542004: 90th percentile AQI 762005: 90th percentile AQI 702006: 90th percentile AQI 672007: 90th percentile AQI 742008: 90th percentile AQI 702009: 90th percentile AQI 692010: 90th percentile AQI 592011: 90th percentile AQI 692012: 90th percentile AQI 612013: 90th percentile AQI 692014: 90th percentile AQI 562015: 90th percentile AQI 612016: 90th percentile AQI 522017: 90th percentile AQI 632018: 90th percentile AQI 632019: 90th percentile AQI 582020: 90th percentile AQI 632021: 90th percentile AQI 572022: 90th percentile AQI 632023: 90th percentile AQI 582024: 90th percentile AQI 542025: 90th percentile AQI 571980: Median AQI 601981: Median AQI 561982: Median AQI 521983: Median AQI 501984: Median AQI 511985: Median AQI 471986: Median AQI 461987: Median AQI 431988: Median AQI 501989: Median AQI 471990: Median AQI 471991: Median AQI 391992: Median AQI 371993: Median AQI 331994: Median AQI 351995: Median AQI 301996: Median AQI 321997: Median AQI 271998: Median AQI 301999: Median AQI 432000: Median AQI 502001: Median AQI 482002: Median AQI 432003: Median AQI 282004: Median AQI 512005: Median AQI 462006: Median AQI 402007: Median AQI 422008: Median AQI 432009: Median AQI 432010: Median AQI 362011: Median AQI 372012: Median AQI 382013: Median AQI 402014: Median AQI 362015: Median AQI 392016: Median AQI 332017: Median AQI 382018: Median AQI 372019: Median AQI 362020: Median AQI 362021: Median AQI 362022: Median AQI 362023: Median AQI 382024: Median AQI 352025: Median AQI 371980198519901995200020052010201520202025
  • 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
Ozone18751%
Fine particles (PM2.5)17849%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365283820000375787Ozone
2024366311550000355493Ozone
20233652679710003858117PM2.5
20223652669432003663165PM2.5
20213652947010003657105Ozone
20203662758210263663779Ozone
2019365283820000365891PM2.5
20183652728481003763152Ozone
20173652788115003863166PM2.5
20163663244110003352108Ozone
20153652778602003961167PM2.5
20143652907410003656115PM2.5
201336524511550004069116PM2.5
201236626310210003861106PM2.5
20113652609960003769127PM2.5
2010365283820000365999PM2.5
200936523113130004369133PM2.5
200836622913250004370142PM2.5
200736523811971004274152PM2.5
200636524311561004067178PM2.5
200536520815241004670158PM2.5
200436618117762005176172PM2.5
2003365306590000285493CO
200236523213030004367123PM2.5
200136519216931004870186PM2.5
200036618617532005074185PM2.5
199936521414551004366162PM2.5
1998364354100000304290CO
1997362349130000274565CO
1996363331320000324972CO
1995365333320000305081CO
1994365311540000355496CO
1993365307580000335493CO
1992363290730000376086CO
199136525810340003973120CO
19903652271380000476497CO
198936521214850004770126CO
198836618617730005074111CO
198736524611540004369126CO
198636523412380004673132CO
198536522413920004769103CO
198436617618730005173130CO
1983365187164122005080197CO
198236517318552005274171CO
1981365125216213005691198CO
1980366112235162106095208CO

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 Oregon with a similar median AQI in 2025

All monitored counties in Oregon

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