Metro area air quality · 2025

Sioux City, IA-NE-SD

Median AQI 39 (Good). 79.6% of monitored days rated Good across this metro's EPA monitoring network.

39
Median AQI
79.6%
Good-air days
0
Unhealthy days
67%
Cleaner than US metros

Sioux City, IA-NE-SD posted a 2025 median AQI of 39 (Good) with 79.6% Good days

According to the U.S. EPA Air Quality System, the Sioux City, IA-NE-SD CBSA recorded a median AQI of 39 across 284 monitored days in 2025, with 79.6% rated Good and 0 unhealthy or worse. This is an annual metro comparison, not a live advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US metros
The Sioux City, IA-NE-SD CBSA's 79.6% Good-day share places it cleaner than 67% of US metros in 2025.
Closest median-AQI peer
Bay City, MI (70.4% Good, median AQI 39) is the closest nationwide median-AQI peer to Sioux City, IA-NE-SD.
2020–2025 Good-day shift
Sioux City, IA-NE-SD's Good-day share moved +0.7 points from 2020 to 2025 (median AQI +0).
Median AQI
Median AQI: 39

Aggregated from EPA Air Quality System (2025), 284 monitored days. EPA AQS →

The verdict

Sioux City, IA-NE-SD's Good-day share (79.6%) sits in the middle CBSA tercile on this extract. On the EPA scale the metro runs good, cleaner than the median US metro, with a median AQI of 39 and 79.6% of 284 monitored days in the Good band.

39
median AQI · Good
79.6%
days rated Good
67%
cleaner than US metros
122
worst single reading

No day crossed into the Unhealthy tier across the metro's monitors in 2025.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Sioux City, IA-NE-SD metro's peak single-day AQI rose from 93 to 122 between the 2024 and 2025 EPA annual releases, a change of +29 points.
  • Sioux City, IA-NE-SD metro's Good-day share rose from 78.9% to 80.4% between the 2024 and 2025 EPA annual releases, a change of +1.6 percentage points.
  • Sioux City, IA-NE-SD metro's median AQI fell from 43 to 39 between the 2024 and 2025 EPA annual releases, a change of -4 points.

Compared against 284 monitored days in 2024 and 281 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

Sioux City, IA-NE-SD's Good-day share (79.6%) sits in the middle CBSA tercile on this extract. Signature read: 79.6% Good-day share (mid tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 39 over 284 measured days in 2025 (Good / Good). The monitored-day split lands at 226 Good (80%), 55 Moderate (19%), and 3 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 61; the highest single-day reading hit 122 (USG).

Across 2020–2025, Good-day share shifted +0.7 points and median AQI moved +0 (stable). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Bay City, MI (70.4% good, AQI 39); Brainerd, MN (74.3% good, AQI 39); Cambridge, MD (86.0% good, AQI 39).

Understanding AQI →

Air Quality Summary

Median AQI

39

Good

Good Days

79.6%

226 of 284 days

Max AQI

122

USG

Health Grade

Good

90th pct: 61

AQI Day Breakdown (2025)

Distribution of 284 monitored days across EPA AQI categories.

Good

226

80%

Moderate

55

19%

USG

3

1%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Sioux City, IA-NE-SD metro area's air quality is rated Good based on 79.6% good air days. No unhealthy air days were recorded in 2025.

Air quality is generally acceptable. Unusually sensitive people should monitor real-time conditions at AirNow.gov during high-pollution events.

How does the Sioux City, IA-NE-SD metro compare?

How Sioux City, IA-NE-SD compares

Good-day share better than typical
Sioux City, IA-NE-SD 79.6%
Bay City, MI 70.4%
Typical US metro 70.6%
Median AQI better than typical
Sioux City, IA-NE-SD 39
Bay City, MI 39
Typical US metro 41
Unhealthy days / yr better than typical
Sioux City, IA-NE-SD 0
Bay City, MI 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is stable in the Sioux City, IA-NE-SD metro. Highest Good-day share: 2022 (80.5%, 91 of 113 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 291 74 0 39
2021 194 105 2 45
2022 91 22 0 36
2023 71 45 2 43
2024 224 60 0 43
2025 226 55 0 39

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Sioux City, IA-NE-SD (39).

Bay City, MI

Median AQI 39 · 70.4% Good-day share

39

Brainerd, MN

Median AQI 39 · 74.3% Good-day share

39

Cambridge, MD

Median AQI 39 · 86.0% Good-day share

39

Charleston, WV

Median AQI 39 · 77.0% Good-day share

39

Dalton, GA

Median AQI 39 · 90.3% Good-day share

39

Harrisonburg, VA

Median AQI 39 · 80.0% Good-day share

39

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Sioux City, IA-NE-SD's 0 (independent of median AQI).

Aberdeen, SD

0 unhealthy-or-worse days · median AQI 27

27

Aberdeen, WA

0 unhealthy-or-worse days · median AQI 22

22

Adrian, MI

0 unhealthy-or-worse days · median AQI 41

41

Akron, OH

0 unhealthy-or-worse days · median AQI 45

45

Albany, GA

0 unhealthy-or-worse days · median AQI 46

46

Albany, OR

0 unhealthy-or-worse days · median AQI 27

27

Frequently Asked Questions

How many unhealthy air days does Sioux City, IA-NE-SD have? ▼
In 2025, the Sioux City, IA-NE-SD metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 122.
What is the air quality in the Sioux City, IA-NE-SD metro area? ▼
The Sioux City, IA-NE-SD metro area has a median Air Quality Index (AQI) of 39, rated "Good." 79.6% of monitored days (226 out of 284) had good air quality in 2025.
Is air quality in Sioux City, IA-NE-SD getting better or worse? ▼
Air quality in the Sioux City, IA-NE-SD metro is stable across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 80.5% (91 of 113 days). Lowest qualifying Good-day share: 2023 at 60.2% (71 of 118 days).
What does AQI 39 mean for health? ▼
An AQI of 39 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
How does Sioux City, IA-NE-SD compare to other metro areas? ▼
The Sioux City, IA-NE-SD metro has 79.6% good air days. Similar metros: Bay City, MI (70.4% good), Brainerd, MN (74.3% good), Cambridge, MD (86.0% good).
What is the 90th percentile AQI for Sioux City, IA-NE-SD? ▼
The 90th percentile AQI for the Sioux City, IA-NE-SD metro area is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 122 (USG).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Sioux City, IA-NE-SD, 2025. See our methodology for how AQI, median, and coverage figures are computed.

Read our methodology , how this data is sourced, computed, and verified.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary, Sioux City, IA-NE-SD · 2020–2025