Metro area air quality · 2025

Decatur, AL

Median AQI 41 (Good). 78.4% of monitored days rated Good across this metro's EPA monitoring network.

Compiled by PlainAirData · August 23, 2026

41
Median AQI: 78.4%
Good-air days: 0
Unhealthy days: 64%
Cleaner than US metros

Decatur, AL posted a 2025 median AQI of 41 (Good) with 78.4% Good days

According to the U.S. EPA Air Quality System, the Decatur, AL CBSA recorded a median AQI of 41 across 365 monitored days in 2025, with 78.4% 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 Decatur, AL CBSA's 78.4% Good-day share places it cleaner than 64% of US metros in 2025.
Closest median-AQI peer: Adrian, MI (69.3% Good, median AQI 41) is the closest nationwide median-AQI peer to Decatur, AL.
2020–2025 Good-day shift: Decatur, AL's Good-day share moved +7.8 points from 2020 to 2025 (median AQI +0).
Median AQI: Median AQI: 41

Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →

The verdict

Decatur, AL's peak reading 71 stays in the lower max-AQI tercile on this extract. On the EPA scale the metro runs good, cleaner than the median US metro, with a median AQI of 41 and 78.4% of 365 monitored days in the Good band.

41
median AQI · Good: 78.4%
days rated Good: 64%
cleaner than US metros: 71
worst single reading

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

Decatur, AL metro's Good-day share rose from 72.1% to 78.4% between the 2024 and 2025 EPA annual releases, a change of +6.2 percentage points.
Decatur, AL metro's peak single-day AQI fell from 86 to 71 between the 2024 and 2025 EPA annual releases, a change of -15 points.
Decatur, AL metro's median AQI fell from 44 to 41 between the 2024 and 2025 EPA annual releases, a change of -3 points.

Decatur, AL's peak reading 71 stays in the lower max-AQI tercile on this extract. Signature read: peak AQI 71 (low tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 41 over 365 measured days in 2025 (Good / Good). The monitored-day split lands at 286 Good (78%), 79 Moderate (22%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 55; the highest single-day reading hit 71 (Moderate).

Across 2020–2025, Good-day share shifted +7.8 points and median AQI moved +0 (improving). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Adrian, MI (69.3% good, AQI 41); Albany-Schenectady-Troy, NY (67.7% good, AQI 41); Ann Arbor, MI (69.3% good, AQI 41).

Understanding AQI →

Air Quality Summary

Median AQI

Good

Good Days

78.4%

286 of 365 days

Max AQI

Moderate

Health Grade

Good

90th pct: 55

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

286

78%

Moderate

22%

USG

Unhealthy

Very Unhealthy

Hazardous

Health Impact Assessment

Good

The Decatur, AL metro area's air quality is rated Good based on 78.4% 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 Decatur, AL metro compare?

How Decatur, AL compares

Compare against

Good-day share better than typical

Decatur, AL 78.4%

Adrian, MI 69.3%

Typical US metro 70.6%

Median AQI about typical

Decatur, AL 41

Adrian, MI 41

Typical US metro 41

Unhealthy days / yr better than typical

Decatur, AL 0

Adrian, MI 0

Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Decatur, AL metro. Highest Good-day share: 2025 (78.4%, 286 of 365 monitored days).

Year	Good	Moderate	Median AQI	Max AQI
2020	252	105	41	78
2021	208	157	47	97
2022	208	156	47	111
2023	257	106	43	140
2024	264	102	44	86
2025	286	79	41	71

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Decatur, AL (41).

Adrian, MI

Median AQI 41 · 69.3% Good-day share

Albany-Schenectady-Troy, NY

Median AQI 41 · 67.7% Good-day share

Ann Arbor, MI

Median AQI 41 · 69.3% Good-day share

Bowling Green, KY

Median AQI 41 · 75.6% Good-day share

Brunswick, GA

Median AQI 41 · 74.3% Good-day share

Dover, DE

Median AQI 41 · 75.6% Good-day share

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Decatur, AL's 0 (independent of median AQI).

Aberdeen, SD

0 unhealthy-or-worse days · median AQI 27

Aberdeen, WA

0 unhealthy-or-worse days · median AQI 22

Akron, OH

0 unhealthy-or-worse days · median AQI 45

Albany, GA

0 unhealthy-or-worse days · median AQI 46

Albany, OR

0 unhealthy-or-worse days · median AQI 27

Alexandria, LA

0 unhealthy-or-worse days · median AQI 37

Frequently Asked Questions

What is the 90th percentile AQI for Decatur, AL? ▼

The 90th percentile AQI for the Decatur, AL metro area is 55, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 71 (Moderate).

How many unhealthy air days does Decatur, AL have? ▼

In 2025, the Decatur, AL metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 71.

What is the air quality in the Decatur, AL metro area? ▼

The Decatur, AL metro area has a median Air Quality Index (AQI) of 41, rated "Good." 78.4% of monitored days (286 out of 365) had good air quality in 2025.

Is air quality in Decatur, AL getting better or worse? ▼

Air quality in the Decatur, AL metro is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 78.4% (286 of 365 days). Lowest qualifying Good-day share: 2021 at 57.0% (208 of 365 days).

What does AQI 41 mean for health? ▼

An AQI of 41 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 Decatur, AL compare to other metro areas? ▼

The Decatur, AL metro has 78.4% good air days. Similar metros: Adrian, MI (69.3% good), Albany-Schenectady-Troy, NY (67.7% good), Ann Arbor, MI (69.3% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Decatur, AL, 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, Decatur, AL · 2020–2025 Accessed 2026-07-06