EnviroNearby

Rosebud County, Montana air quality history

Daily Air Quality Index summaries from EPA monitors in Rosebud, Montana, 1980–2025.

96%
Good days in 2024
4
Median daily AQI, 2024
0
Days above 100 in 2024
366
Days with an AQI in 2024 (of 366)

In 2024, EPA reported a daily Air Quality Index (AQI) for Rosebud, Montana on 366 days. 353 of those days (96%) were in the Good range, and the median daily AQI was 4. That median is lower than the typical monitored county in Montana (median 24 across 19 counties), and lower than the typical monitored U.S. county (41). The main pollutant was nitrogen dioxide (NO₂) on 190 days. Across the years with fuller monitoring, the share of Good days rose: an average of 93% in 1980–1982 versus 98% in 2022–2024.

Years with fewer than 120 monitored days (2025) 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%1980: Good 258 of 320 days1980: Moderate 62 of 320 days19801981: Good 352 of 355 days1981: Moderate 3 of 355 days1982: Good 357 of 365 days1982: Moderate 6 of 365 days1982: Unhealthy for Sensitive Groups 1 of 365 days1982: Unhealthy 1 of 365 days1983: Good 350 of 364 days1983: Moderate 14 of 364 days1984: Good 365 of 366 days1984: Moderate 1 of 366 days1985: Good 363 of 365 days1985: Moderate 2 of 365 days19851986: Good 364 of 365 days1986: Unhealthy for Sensitive Groups 1 of 365 days1987: Good 365 of 365 days1988: Good 364 of 366 days1988: Moderate 2 of 366 days1989: Good 355 of 365 days1989: Moderate 8 of 365 days1989: Unhealthy for Sensitive Groups 2 of 365 days1990: Good 334 of 365 days1990: Moderate 29 of 365 days1990: Unhealthy for Sensitive Groups 2 of 365 days19901991: Good 336 of 365 days1991: Moderate 28 of 365 days1991: Unhealthy for Sensitive Groups 1 of 365 days1992: Good 349 of 366 days1992: Moderate 16 of 366 days1992: Unhealthy for Sensitive Groups 1 of 366 days1993: Good 346 of 365 days1993: Moderate 19 of 365 days1994: Good 324 of 365 days1994: Moderate 40 of 365 days1994: Unhealthy for Sensitive Groups 1 of 365 days1995: Good 341 of 365 days1995: Moderate 23 of 365 days1995: Unhealthy for Sensitive Groups 1 of 365 days19951996: Good 352 of 366 days1996: Moderate 14 of 366 days1997: Good 349 of 365 days1997: Moderate 14 of 365 days1997: Unhealthy for Sensitive Groups 2 of 365 days1998: Good 338 of 365 days1998: Moderate 26 of 365 days1998: Unhealthy for Sensitive Groups 1 of 365 days1999: Good 313 of 365 days1999: Moderate 52 of 365 days2000: Good 314 of 366 days2000: Moderate 52 of 366 days20002001: Good 302 of 365 days2001: Moderate 62 of 365 days2001: Unhealthy for Sensitive Groups 1 of 365 days2002: Good 315 of 365 days2002: Moderate 47 of 365 days2002: Unhealthy for Sensitive Groups 3 of 365 days2003: Good 312 of 363 days2003: Moderate 49 of 363 days2003: Unhealthy for Sensitive Groups 2 of 363 days2004: Good 350 of 364 days2004: Moderate 14 of 364 days2005: Good 294 of 323 days2005: Moderate 28 of 323 days2005: Unhealthy for Sensitive Groups 1 of 323 days20052006: Good 292 of 308 days2006: Moderate 16 of 308 days2007: Good 332 of 348 days2007: Moderate 16 of 348 days2008: Good 354 of 360 days2008: Moderate 6 of 360 days2009: Good 341 of 365 days2009: Moderate 21 of 365 days2009: Unhealthy for Sensitive Groups 3 of 365 days2010: Good 334 of 365 days2010: Moderate 29 of 365 days2010: Unhealthy for Sensitive Groups 2 of 365 days20102011: Good 310 of 365 days2011: Moderate 51 of 365 days2011: Unhealthy for Sensitive Groups 4 of 365 days2012: Good 241 of 365 days2012: Moderate 118 of 365 days2012: Unhealthy for Sensitive Groups 6 of 365 days2013: Good 313 of 365 days2013: Moderate 48 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days2014: Good 293 of 365 days2014: Moderate 69 of 365 days2014: Unhealthy for Sensitive Groups 3 of 365 days2015: Good 274 of 365 days2015: Moderate 82 of 365 days2015: Unhealthy for Sensitive Groups 8 of 365 days2015: Unhealthy 1 of 365 days20152016: Good 307 of 366 days2016: Moderate 58 of 366 days2016: Unhealthy for Sensitive Groups 1 of 366 days2017: Good 277 of 365 days2017: Moderate 77 of 365 days2017: Unhealthy for Sensitive Groups 5 of 365 days2017: Unhealthy 6 of 365 days2018: Good 302 of 365 days2018: Moderate 61 of 365 days2018: Unhealthy for Sensitive Groups 2 of 365 days2019: Good 328 of 365 days2019: Moderate 36 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 321 of 366 days2020: Moderate 40 of 366 days2020: Unhealthy for Sensitive Groups 3 of 366 days2020: Unhealthy 2 of 366 days20202021: Good 266 of 363 days2021: Moderate 83 of 363 days2021: Unhealthy for Sensitive Groups 12 of 363 days2021: Unhealthy 2 of 363 days2022: Good 337 of 337 days2023: Good 279 of 285 days2023: Moderate 5 of 285 days2023: Unhealthy for Sensitive Groups 1 of 285 days2024: Good 353 of 366 days2024: Moderate 13 of 366 days2025: Good 96 of 98 days2025: Moderate 2 of 98 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 611981: 90th percentile AQI 421982: 90th percentile AQI 421983: 90th percentile AQI 461984: 90th percentile AQI 101985: 90th percentile AQI 321986: 90th percentile AQI 281987: 90th percentile AQI 281988: 90th percentile AQI 281989: 90th percentile AQI 351990: 90th percentile AQI 451991: 90th percentile AQI 461992: 90th percentile AQI 381993: 90th percentile AQI 421994: 90th percentile AQI 521995: 90th percentile AQI 431996: 90th percentile AQI 321997: 90th percentile AQI 401998: 90th percentile AQI 471999: 90th percentile AQI 532000: 90th percentile AQI 542001: 90th percentile AQI 562002: 90th percentile AQI 532003: 90th percentile AQI 542004: 90th percentile AQI 392005: 90th percentile AQI 482006: 90th percentile AQI 422007: 90th percentile AQI 392008: 90th percentile AQI 332009: 90th percentile AQI 382010: 90th percentile AQI 492011: 90th percentile AQI 552012: 90th percentile AQI 692013: 90th percentile AQI 542014: 90th percentile AQI 582015: 90th percentile AQI 622016: 90th percentile AQI 552017: 90th percentile AQI 672018: 90th percentile AQI 572019: 90th percentile AQI 512020: 90th percentile AQI 532021: 90th percentile AQI 742022: 90th percentile AQI 142023: 90th percentile AQI 182024: 90th percentile AQI 282025: 90th percentile AQI 271980: Median AQI 401981: Median AQI 291982: Median AQI 311983: Median AQI 361984: Median AQI 11985: Median AQI 181986: Median AQI 171987: Median AQI 181988: Median AQI 181989: Median AQI 191990: Median AQI 221991: Median AQI 221992: Median AQI 211993: Median AQI 191994: Median AQI 211995: Median AQI 171996: Median AQI 161997: Median AQI 201998: Median AQI 231999: Median AQI 272000: Median AQI 242001: Median AQI 302002: Median AQI 242003: Median AQI 232004: Median AQI 192005: Median AQI 212006: Median AQI 192007: Median AQI 182008: Median AQI 172009: Median AQI 172010: Median AQI 352011: Median AQI 392012: Median AQI 442013: Median AQI 392014: Median AQI 392015: Median AQI 402016: Median AQI 382017: Median AQI 392018: Median AQI 382019: Median AQI 362020: Median AQI 372021: Median AQI 382022: Median AQI 22023: Median AQI 32024: Median AQI 42025: Median AQI 111980198519901995200020052010201520202025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2024

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
Nitrogen dioxide (NO₂)19052%
Fine particles (PM2.5)9225%
Coarse particles (PM10)8423%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025989620000112768PM2.5
202436635313000042890NO2
202328527951000318132NO2
20223373370000021436NO2
202136326683122003874155Ozone
20203663214032003753154Ozone
20193653283610003651108Ozone
20183653026120003857133Ozone
20173652777756003967196Ozone
20163663075810003855132Ozone
20153652748281004062156Ozone
20143652936930003958115Ozone
20133653134840003954113Ozone
201236524111860004469145Ozone
20113653105140003955150Ozone
20103653342920003549108Ozone
20093653412130001738123PM10
200836035460000173378PM10
20073483321600001839100PM10
2006308292160000194297PM10
20053232942810002148106PM10
2004364350140000193979PM10
20033633124920002354120PM10
20023653154730002453137PM10
20013653026210003056104PM10
2000366314520000245493PM10
1999365313520000275379PM10
19983653382610002347108PM10
19973653491420002040120NO2
1996366352140000163284NO2
19953653412310001743122NO2
19943653244010002152102PM10
1993365346190000194292PM10
19923663491610002138114PM10
19913653362810002246120PM10
19903653342920002245107PM10
1989365355820001935115NO2
198836636420000182857NO2
198736536500000182837NO2
1986365364010001728102NO2
198536536320000183257NO2
19843663651000011076NO2
1983364350140000364677Ozone
1982365357611003142152Ozone
198135535230000294290Ozone
1980320258620000406197Ozone

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.

All monitored counties in Montana

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