EnviroNearby

Oliver County, North Dakota air quality history

Daily Air Quality Index summaries from EPA monitors in Oliver, North Dakota, 1980–2025.

81%
Good days in 2025
38
Median daily AQI, 2025
11
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 Oliver, North Dakota on 365 days. 295 of those days (81%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in North Dakota (median 38 across 9 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 264 days. Across the years with fuller monitoring, the share of Good days fell: an average of 93% in 1980–1982 versus 76% 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 327 of 362 days1980: Moderate 33 of 362 days1980: Unhealthy for Sensitive Groups 2 of 362 days19801981: Good 333 of 363 days1981: Moderate 22 of 363 days1981: Unhealthy for Sensitive Groups 8 of 363 days1982: Good 349 of 365 days1982: Moderate 16 of 365 days1983: Good 338 of 363 days1983: Moderate 25 of 363 days1984: Good 332 of 359 days1984: Moderate 26 of 359 days1984: Unhealthy for Sensitive Groups 1 of 359 days1985: Good 354 of 364 days1985: Moderate 10 of 364 days19851986: Good 348 of 364 days1986: Moderate 16 of 364 days1987: Good 296 of 348 days1987: Moderate 50 of 348 days1987: Unhealthy for Sensitive Groups 2 of 348 days1988: Good 290 of 366 days1988: Moderate 66 of 366 days1988: Unhealthy for Sensitive Groups 9 of 366 days1988: Unhealthy 1 of 366 days1989: Good 330 of 365 days1989: Moderate 34 of 365 days1989: Unhealthy for Sensitive Groups 1 of 365 days1990: Good 187 of 189 days1990: Moderate 2 of 189 days19901991: Good 281 of 299 days1991: Moderate 18 of 299 days1992: Good 296 of 307 days1992: Moderate 11 of 307 days1993: Good 333 of 336 days1993: Moderate 3 of 336 days1994: Good 356 of 365 days1994: Moderate 9 of 365 days1995: Good 355 of 365 days1995: Moderate 10 of 365 days19951996: Good 356 of 366 days1996: Moderate 10 of 366 days1997: Good 348 of 365 days1997: Moderate 16 of 365 days1997: Unhealthy for Sensitive Groups 1 of 365 days1998: Good 338 of 365 days1998: Moderate 27 of 365 days1999: Good 355 of 365 days1999: Moderate 10 of 365 days2000: Good 359 of 365 days2000: Moderate 6 of 365 days20002001: Good 224 of 229 days2001: Moderate 5 of 229 days2002: Good 358 of 365 days2002: Moderate 7 of 365 days2003: Good 350 of 365 days2003: Moderate 15 of 365 days2004: Good 365 of 366 days2004: Moderate 1 of 366 days2005: Good 356 of 364 days2005: Moderate 8 of 364 days20052006: Good 332 of 365 days2006: Moderate 33 of 365 days2007: Good 353 of 365 days2007: Moderate 12 of 365 days2008: Good 352 of 366 days2008: Moderate 14 of 366 days2009: Good 354 of 365 days2009: Moderate 11 of 365 days2010: Good 343 of 362 days2010: Moderate 19 of 362 days20102011: Good 346 of 365 days2011: Moderate 19 of 365 days2012: Good 308 of 366 days2012: Moderate 58 of 366 days2013: Good 314 of 365 days2013: Moderate 51 of 365 days2014: Good 325 of 365 days2014: Moderate 39 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 305 of 365 days2015: Moderate 53 of 365 days2015: Unhealthy for Sensitive Groups 6 of 365 days2015: Unhealthy 1 of 365 days20152016: Good 351 of 366 days2016: Moderate 15 of 366 days2017: Good 295 of 361 days2017: Moderate 65 of 361 days2017: Unhealthy 1 of 361 days2018: Good 286 of 360 days2018: Moderate 71 of 360 days2018: Unhealthy for Sensitive Groups 3 of 360 days2019: Good 330 of 365 days2019: Moderate 35 of 365 days2020: Good 330 of 366 days2020: Moderate 36 of 366 days20202021: Good 251 of 365 days2021: Moderate 99 of 365 days2021: Unhealthy for Sensitive Groups 9 of 365 days2021: Unhealthy 6 of 365 days2022: Good 268 of 364 days2022: Moderate 96 of 364 days2023: Good 244 of 365 days2023: Moderate 102 of 365 days2023: Unhealthy for Sensitive Groups 11 of 365 days2023: Unhealthy 7 of 365 days2023: Hazardous 1 of 365 days2024: Good 299 of 366 days2024: Moderate 60 of 366 days2024: Unhealthy for Sensitive Groups 5 of 366 days2024: Unhealthy 2 of 366 days2025: Good 295 of 365 days2025: Moderate 59 of 365 days2025: Unhealthy for Sensitive Groups 7 of 365 days2025: Unhealthy 3 of 365 days2025: Very Unhealthy 1 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 491981: 90th percentile AQI 491982: 90th percentile AQI 471983: 90th percentile AQI 481984: 90th percentile AQI 491985: 90th percentile AQI 441986: 90th percentile AQI 471987: 90th percentile AQI 581988: 90th percentile AQI 771989: 90th percentile AQI 501990: 90th percentile AQI 451991: 90th percentile AQI 491992: 90th percentile AQI 451993: 90th percentile AQI 421994: 90th percentile AQI 461995: 90th percentile AQI 451996: 90th percentile AQI 451997: 90th percentile AQI 461998: 90th percentile AQI 481999: 90th percentile AQI 442000: 90th percentile AQI 452001: 90th percentile AQI 462002: 90th percentile AQI 442003: 90th percentile AQI 462004: 90th percentile AQI 402005: 90th percentile AQI 442006: 90th percentile AQI 492007: 90th percentile AQI 462008: 90th percentile AQI 482009: 90th percentile AQI 462010: 90th percentile AQI 472011: 90th percentile AQI 482012: 90th percentile AQI 552013: 90th percentile AQI 532014: 90th percentile AQI 512015: 90th percentile AQI 582016: 90th percentile AQI 462017: 90th percentile AQI 562018: 90th percentile AQI 612019: 90th percentile AQI 502020: 90th percentile AQI 502021: 90th percentile AQI 712022: 90th percentile AQI 592023: 90th percentile AQI 742024: 90th percentile AQI 612025: 90th percentile AQI 581980: Median AQI 321981: Median AQI 331982: Median AQI 341983: Median AQI 371984: Median AQI 351985: Median AQI 351986: Median AQI 341987: Median AQI 341988: Median AQI 361989: Median AQI 271990: Median AQI 71991: Median AQI 331992: Median AQI 241993: Median AQI 241994: Median AQI 311995: Median AQI 331996: Median AQI 351997: Median AQI 371998: Median AQI 341999: Median AQI 352000: Median AQI 322001: Median AQI 342002: Median AQI 312003: Median AQI 322004: Median AQI 302005: Median AQI 322006: Median AQI 342007: Median AQI 332008: Median AQI 352009: Median AQI 342010: Median AQI 372011: Median AQI 352012: Median AQI 382013: Median AQI 382014: Median AQI 362015: Median AQI 372016: Median AQI 332017: Median AQI 392018: Median AQI 392019: Median AQI 362020: Median AQI 362021: Median AQI 412022: Median AQI 402023: Median AQI 422024: Median AQI 382025: Median AQI 381980198519901995200020052010201520202025
  • 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
Ozone26472%
Fine particles (PM2.5)10128%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652955973103858242Ozone
20243662996052003861162Ozone
2023365244102117014274323Ozone
2022364268960000405987PM2.5
20213652519996004171172Ozone
2020366330360000365074Ozone
2019365330350000365084Ozone
20183602867130003961122Ozone
20173612956501003956166Ozone
2016366351150000334692Ozone
20153653055361003758153Ozone
20143653253910003651127Ozone
2013365314510000385384Ozone
2012366308580000385576Ozone
2011365346190000354874Ozone
2010362343190000374793Ozone
2009365354110000344674Ozone
2008366352140000354887Ozone
2007365353120000334680Ozone
2006365332330000344987Ozone
200536435680000324464Ozone
200436636510000304051Ozone
2003365350150000324690Ozone
200236535870000314471Ozone
200122922450000344684Ozone
200036535960000324554Ozone
1999365355100000354497Ozone
1998365338270000344877Ozone
19973653481610003746101Ozone
1996366356100000354574Ozone
1995365355100000334561Ozone
199436535690000314664Ozone
199333633330000244254Ozone
19923072961100002445100Ozone
1991299281180000334974Ozone
19901891872000074567NO2
19893653303410002750108Ozone
19883662906691003677151Ozone
19873482965020003458140Ozone
1986364348160000344790Ozone
1985364354100000354480Ozone
19843593322610003549101Ozone
1983363338250000374890Ozone
1982365349160000344795Ozone
19813633332280003349126Ozone
19803623273320003249143Ozone

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 North Dakota with a similar median AQI in 2025

All monitored counties in North Dakota

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