EnviroNearby

Grand County, Utah air quality history

Daily Air Quality Index summaries from EPA monitors in Grand, Utah, 1984–2025.

60%
Good days in 2025
47
Median daily AQI, 2025
0
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Grand, Utah on 364 days. 219 of those days (60%) were in the Good range, and the median daily AQI was 47. That median is about the same as the typical monitored county in Utah (median 45 across 15 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 203 days. Across the years with fuller monitoring, the share of Good days fell: an average of 85% in 1988–1990 versus 59% in 2023–2025.

Years with fewer than 120 monitored days (1998, 1999, 2000, 2001, 2002, 2003…) 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%1984: Good 94 of 94 days19841987: Good 51 of 51 days1988: Good 199 of 239 days1988: Moderate 40 of 239 days19881989: Good 220 of 294 days1989: Moderate 73 of 294 days1989: Unhealthy for Sensitive Groups 1 of 294 days1990: Good 304 of 317 days1990: Moderate 13 of 317 days19901991: Good 229 of 246 days1991: Moderate 16 of 246 days1991: Unhealthy for Sensitive Groups 1 of 246 days1992: Good 152 of 187 days1992: Moderate 35 of 187 days19921993: Good 4 of 9 days1993: Moderate 5 of 9 days1994: Good 51 of 57 days1994: Moderate 6 of 57 days19941995: Good 56 of 59 days1995: Moderate 3 of 59 days1996: Good 55 of 56 days1996: Moderate 1 of 56 days19961997: Good 54 of 54 days1998: Good 55 of 55 days19981999: Good 47 of 49 days1999: Moderate 2 of 49 days2000: Good 56 of 57 days2000: Moderate 1 of 57 days20002001: Good 59 of 59 days2002: Good 61 of 61 days20022003: Good 27 of 28 days2003: Moderate 1 of 28 days2023: Good 144 of 261 days2023: Moderate 117 of 261 days20232024: Good 229 of 365 days2024: Moderate 134 of 365 days2024: Unhealthy for Sensitive Groups 2 of 365 days2025: Good 219 of 364 days2025: Moderate 145 of 364 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 year0501001984: 90th percentile AQI 321987: 90th percentile AQI 411988: 90th percentile AQI 581989: 90th percentile AQI 641990: 90th percentile AQI 391991: 90th percentile AQI 431992: 90th percentile AQI 611993: 90th percentile AQI 661994: 90th percentile AQI 511995: 90th percentile AQI 451996: 90th percentile AQI 351997: 90th percentile AQI 331998: 90th percentile AQI 341999: 90th percentile AQI 412000: 90th percentile AQI 332001: 90th percentile AQI 302002: 90th percentile AQI 332003: 90th percentile AQI 352023: 90th percentile AQI 642024: 90th percentile AQI 612025: 90th percentile AQI 641984: Median AQI 221987: Median AQI 351988: Median AQI 431989: Median AQI 441990: Median AQI 291991: Median AQI 281992: Median AQI 431993: Median AQI 511994: Median AQI 201995: Median AQI 211996: Median AQI 201997: Median AQI 201998: Median AQI 191999: Median AQI 192000: Median AQI 172001: Median AQI 182002: Median AQI 202003: Median AQI 172023: Median AQI 492024: Median AQI 482025: Median AQI 4719841988199019921994199619982000200220232025
  • 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
Ozone20356%
Fine particles (PM2.5)16144%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253642191450000476496Ozone
202436522913420004861105Ozone
20232611441170000496480Ozone
2003282710000173557PM10
2002616100000203339PM10
2001595900000183041PM10
2000575610000173352PM10
1999494720000194154PM10
1998555500000193450PM10
1997545400000203348PM10
1996565510000203555PM10
1995595630000214581PM10
1994575160000205156PM10
19939450000516666PM10
1992187152350000436197Ozone
19912462291610002843114Ozone
1990317304130000293965Ozone
19892942207310004464115Ozone
1988239199400000435890Ozone
1987515100000354146Ozone
1984949400000223240CO

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 Utah with a similar median AQI in 2025

All monitored counties in Utah

Source: U.S. EPA AirData, “Annual AQI by County” files for 1984–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem