Minnesota · County air quality · 2025

Saint Louis County, Minnesota

Median AQI 42 (Good). 66.6% of monitored days rated Good, direct from EPA Air Quality System stations.

42
Median AQI
66.6%
Good-air days
12
Unhealthy days
26%
Cleaner than US counties

Saint Louis County's 2025 annual median AQI is 42 (Good), with 66.6% Good days

According to the U.S. EPA Air Quality System, Saint Louis County, Minnesota posted a 2025 median AQI of 42 (Good) across 365 monitored days, with 66.6% rated Good and 12 unhealthy or worse. This is an annual comparison, not today's advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US
Saint Louis County's 66.6% Good-day share places it cleaner than 26% of US counties in 2025.
Closest median-AQI peer
Ada County (74.0% Good, median AQI 42) is the closest nationwide median-AQI peer to Saint Louis County.
2020–2025 trend
Saint Louis County's floor-qualifying Good-day share is worsening from 2020 to 2025 (76.2% → 66.8%).
Median AQI
Median AQI: 42

According to the 2025 EPA AQS county release on PlainAirData, Saint Louis County, Minnesota ranks #581 of 951 by median AQI (42) and #707 by good-day share (66.6%). 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
  • Saint Louis County's Good-day share fell from 78.1% to 66.6% between the 2024 and 2025 EPA annual releases, a change of -11.6 percentage points.
  • Saint Louis County's Unhealthy-category days rose from 0 to 11 between the 2024 and 2025 EPA annual releases, a change of +11 days.
  • Saint Louis County's peak single-day AQI rose from 114 to 216 between the 2024 and 2025 EPA annual releases, a change of +102 points.
  • Saint Louis County's median AQI rose from 39 to 42 between the 2024 and 2025 EPA annual releases, a change of +3 points.

Compared against 366 monitored days in 2024 and 365 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

Saint Louis 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 365 monitored days G M Median AQI 42 0 50 100 150 200 300 500 Saint Louis County
  • Good · 243 d · 66.6%
  • Moderate · 99 d · 27.1%
  • USG · 11 d · 3.0%
  • Unhealthy · 11 d · 3.0%
  • Very Unhealthy · 1 d · 0.3%

How did Saint Louis County's air break down in 2025?

Across 365 monitored days, 243 fell in the Good band (AQI 0–50) and 12 reached Unhealthy or worse. The worst single day peaked at AQI 216 (Very Unhealthy).

EPA AQS →
Saint Louis County, Good days share 66.6%
National avg

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

Saint Louis County, Unhealthy-or-worse share 32.9%
National avg

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

Where Saint Louis County sits nationally

COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Saint Louis County's Good-day share is 66.6% - cleaner than 26% of that comparison set.

Saint Louis County Good-day share vs. every US county

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

66.6% 26th percentile higher than 26% 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%). Below this entry. 65.0%–70.0%: 93 US counties (10%). This entry sits in this band. 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 Saint Louis County.

Saint Louis County, Minnesota 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. PM2.5 · 50.7% Ozone · 49.3% 0% 25% 50% 75% 100% Saint Louis County, Minnesota · 365 monitored days Criteria pollutant column
  • PM2.5 · 185 days · 50.7%
  • Ozone · 180 days · 49.3%

2024 daily-monitor rhythm in Saint Louis County

Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Jul posted the highest typical readings (median AQI 52, peak 74); Nov was cleanest at median 31. Summer months (Jun–Aug) averaged median AQI 47 vs 34 in Dec–Feb.

0 10 20 30 40 50 60 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 35 35 39 43 39 39 52 51 43 33 31 32
Saint Louis County median daily AQI by calendar month (2024, EPA daily county file)

Five-year seasonal record

EPA day-level county files · 2020–2024

1,827 daily readings show a recurring local pattern: Jun has the highest matched-month median AQI (48), while Oct is lowest (32). Each cell is that month’s median daily AQI, not a current-air forecast.

JanFebMarAprMayJunJulAugSepOctNovDec
2020 435044404141373329444135
2021 373739383946644132263133
2022 373740404240323127333133
2023 364243445274525654263132
2024 353539433939525143333132

Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.

Health Impact Assessment

Moderate

Saint Louis County's air quality is rated Moderate based on 66.6% good air days. There were 12 unhealthy days in 2025 when outdoor activity should be limited.

Air quality reached unhealthy levels on 12 days in 2025 (11 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.

Sensitive group advisory

People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.

The dominant pollutant is PM2.5, driving AQI on 185 of 365 monitored days.

5-Year Air Quality Trend

Air quality is worsening in Saint Louis County. Highest Good-day share: 2022 (88.2%, 322 of 365 monitored days).

Year Good Moderate USG Unhealthy Median AQI
2020 279 86 1 0 40
2021 283 72 8 2 37
2022 322 43 0 0 36
2023 221 136 6 1 44
2024 286 77 3 0 39
2025 243 99 11 11 42

How does Saint Louis County compare?

How Saint Louis County compares

Good-day share worse than typical
Saint Louis County 66.6%
Ada County, Idaho 74.0%
Typical US county 76.0%
Median AQI worse than typical
Saint Louis County 42
Ada County, Idaho 42
Typical US county 39
Unhealthy days / yr worse than typical
Saint Louis County 12
Ada 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 Saint Louis County, Minnesota · 2020–2025

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Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.

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.