Utah · County air quality · 2025

Grand County, Utah

Median AQI 47 (Good). 60.2% of monitored days rated Good, direct from EPA Air Quality System stations.

47
Median AQI
60.2%
Good-air days
0
Unhealthy days
15%
Cleaner than US counties

Grand County's 2025 annual median AQI is 47 (Good), with 60.2% Good days

According to the U.S. EPA Air Quality System, Grand County, Utah posted a 2025 median AQI of 47 (Good) across 364 monitored days, with 60.2% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US
Grand County's 60.2% Good-day share places it cleaner than 15% of US counties in 2025.
Closest median-AQI peer
Bonner County (56.2% Good, median AQI 47) is the closest nationwide median-AQI peer to Grand County.
2023–2025 trend
Grand County's floor-qualifying Good-day share is improving from 2023 to 2025 (55.2% → 60.2%).
Median AQI
Median AQI: 47

According to the 2025 EPA AQS county release on PlainAirData, Grand County, Utah ranks #818 of 951 by median AQI (47) and #805 by good-day share (60.2%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Grand County's Good-day share fell from 67.4% to 60.2% between the 2024 and 2025 EPA annual releases, a change of -7.2 percentage points.

Compared against 365 monitored days in 2024 and 364 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Data updated August 2026

Grand County AQI category distribution Stacked-segment bar showing the share of monitored days that fell in each EPA AQI category, Good, Moderate, USG, Unhealthy, Very Unhealthy, Hazardous, with median AQI marker. AQI category distribution 364 monitored days G M Median AQI 47 0 50 100 150 200 300 500 Grand County
  • Good · 219 d · 60.2%
  • Moderate · 145 d · 39.8%

How did Grand County's air break down in 2025?

Across 364 monitored days, 219 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 96 (Moderate).

EPA AQS →
Grand County, Good days share 60.2%
National avg

Share of monitored days at AQI 0-50 (Good band).

Grand County, Unhealthy-or-worse share 0.0%
National avg

Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).

Where Grand County sits nationally

COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Grand County's Good-day share is 60.2% - cleaner than 15% of that comparison set.

Grand County Good-day share vs. every US county

Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release

60.2% 15th percentile higher than 15% of 951 US counties

0.0%–5.0%: 0 US counties (0%). Below this entry. 5.0%–10.0%: 1 US counties (0%). Below this entry. 10.0%–15.0%: 4 US counties (0%). Below this entry. 15.0%–20.0%: 4 US counties (0%). Below this entry. 20.0%–25.0%: 1 US counties (0%). Below this entry. 25.0%–30.0%: 5 US counties (1%). Below this entry. 30.0%–35.0%: 9 US counties (1%). Below this entry. 35.0%–40.0%: 4 US counties (0%). Below this entry. 40.0%–45.0%: 16 US counties (2%). Below this entry. 45.0%–50.0%: 16 US counties (2%). Below this entry. 50.0%–55.0%: 32 US counties (3%). Below this entry. 55.0%–60.0%: 50 US counties (5%). Below this entry. 60.0%–65.0%: 77 US counties (8%). This entry sits in this band. 65.0%–70.0%: 93 US counties (10%). Above this entry. 70.0%–75.0%: 109 US counties (11%). Above this entry. 75.0%–80.0%: 114 US counties (12%). Above this entry. 80.0%–85.0%: 123 US counties (13%). Above this entry. 85.0%–90.0%: 99 US counties (10%). Above this entry. 90.0%–95.0%: 117 US counties (12%). Above this entry. 95.0%–100.0%: 70 US counties (7%). Above this entry. 100.0%–105.0%: 7 US counties (1%). Above this entry. This county 0.0% 100% every floor-qualified US county, bucketed by value

Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025

Pollutant Breakdown

Days where each pollutant was the primary driver of AQI readings in Grand County.

Grand County, Utah criteria pollutant distribution Stratified-band visualization showing the share of monitored days each criteria pollutant (PM2.5, PM10, O3, NO2, CO) was the primary AQI driver. Ozone · 55.8% PM2.5 · 44.2% 0% 25% 50% 75% 100% Grand County, Utah · 364 monitored days Criteria pollutant column
  • Ozone · 203 days · 55.8%
  • PM2.5 · 161 days · 44.2%

2024 daily-monitor rhythm in Grand County

Month-by-month median AQI from EPA day-level county monitors (365 reported days in 2024). Jul posted the highest typical readings (median AQI 60, peak 105); Jan was cleanest at median 38. Summer months (Jun–Aug) averaged median AQI 52 vs 42 in Dec–Feb.

0 10 20 30 40 50 60 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 38 39 42 47 51 50 60 46 47 52 43 49
Grand County median daily AQI by calendar month (2024, EPA daily county file)

Health Impact Assessment

Moderate

Grand County's air quality is rated Moderate based on 60.2% good air days. No unhealthy air days were recorded in 2025.

Air quality was acceptable on 60.2% of monitored days in 2025, with a median AQI of 47. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.

The dominant pollutant is Ozone, driving AQI on 203 of 364 monitored days.

5-Year Air Quality Trend

Air quality is improving in Grand County. Highest Good-day share: 2024 (67.4%, 246 of 365 monitored days).

Year Good Moderate USG Unhealthy Median AQI
2023 144 117 0 0 49
2024 246 117 2 0 47
2025 219 145 0 0 47

How does Grand County compare?

How Grand County compares

Good-day share worse than typical
Grand County 60.2%
Bonner County, Idaho 56.2%
Typical US county 76.0%
Median AQI worse than typical
Grand County 47
Bonner County, Idaho 47
Typical US county 39
Unhealthy days / yr better than typical
Grand County 0
Bonner County, Idaho 0
Typical US county 1

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Grand County, Utah · 2020–2025

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Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.