Metro area air quality · 2025

Williamsport, PA

Median AQI 40 (Good). 77.5% of monitored days rated Good across this metro's EPA monitoring network.

40
Median AQI
77.5%
Good-air days
0
Unhealthy days
62%
Cleaner than US metros

Williamsport, PA posted a 2025 median AQI of 40 (Good) with 77.5% Good days

According to the U.S. EPA Air Quality System, the Williamsport, PA CBSA recorded a median AQI of 40 across 364 monitored days in 2025, with 77.5% 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 Williamsport, PA CBSA's 77.5% Good-day share places it cleaner than 62% of US metros in 2025.
Closest median-AQI peer
Altoona, PA (76.9% Good, median AQI 40) is the closest nationwide median-AQI peer to Williamsport, PA.
2020–2025 Good-day shift
Williamsport, PA's Good-day share moved +0.2 points from 2020 to 2025 (median AQI -1).
Median AQI
Median AQI: 40

Aggregated from EPA Air Quality System (2025), 364 monitored days. EPA AQS →

The verdict

Williamsport, PA's Good-day share (77.5%) 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 40 and 77.5% of 364 monitored days in the Good band.

40
median AQI · Good
77.5%
days rated Good
62%
cleaner than US metros
105
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
  • Williamsport, PA metro's peak single-day AQI fell from 122 to 105 between the 2024 and 2025 EPA annual releases, a change of -17 points.

Compared against 365 monitored days in 2024 and 363 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

Williamsport, PA's Good-day share (77.5%) sits in the middle CBSA tercile on this extract. Signature read: 77.5% 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 40 over 364 measured days in 2025 (Good / Good). The monitored-day split lands at 282 Good (77%), 81 Moderate (22%), and 1 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 61; the highest single-day reading hit 105 (USG).

Across 2020–2025, Good-day share shifted +0.2 points and median AQI moved -1 (stable). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Altoona, PA (76.9% good, AQI 40); Beaver Dam, WI (72.3% good, AQI 40); Bismarck, ND (76.7% good, AQI 40).

Understanding AQI →

Air Quality Summary

Median AQI

40

Good

Good Days

77.5%

282 of 364 days

Max AQI

105

USG

Health Grade

Good

90th pct: 61

AQI Day Breakdown (2025)

Distribution of 364 monitored days across EPA AQI categories.

Good

282

77%

Moderate

81

22%

USG

1

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Williamsport, PA metro area's air quality is rated Good based on 77.5% 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 Williamsport, PA metro compare?

How Williamsport, PA compares

Good-day share better than typical
Williamsport, PA 77.5%
Altoona, PA 76.9%
Typical US metro 70.6%
Median AQI better than typical
Williamsport, PA 40
Altoona, PA 40
Typical US metro 41
Unhealthy days / yr better than typical
Williamsport, PA 0
Altoona, PA 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is stable in the Williamsport, PA metro. Highest Good-day share: 2023 (86.4%, 242 of 280 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 283 82 0 41
2021 221 132 0 44
2022 221 83 0 40
2023 242 38 0 38
2024 281 84 0 39
2025 282 81 0 40

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Williamsport, PA (40).

Altoona, PA

Median AQI 40 · 76.9% Good-day share

40

Beaver Dam, WI

Median AQI 40 · 72.3% Good-day share

40

Bismarck, ND

Median AQI 40 · 76.7% Good-day share

40

Cape Coral-Fort Myers, FL

Median AQI 40 · 76.4% Good-day share

40

College Station-Bryan, TX

Median AQI 40 · 68.5% Good-day share

40

Fallon, NV

Median AQI 40 · 85.2% Good-day share

40

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Williamsport, PA'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 Williamsport, PA have? ▼
In 2025, the Williamsport, PA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
What is the air quality in the Williamsport, PA metro area? ▼
The Williamsport, PA metro area has a median Air Quality Index (AQI) of 40, rated "Good." 77.5% of monitored days (282 out of 364) had good air quality in 2025.
Is air quality in Williamsport, PA getting better or worse? ▼
Air quality in the Williamsport, PA 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: 2023 at 86.4% (242 of 280 days). Lowest qualifying Good-day share: 2021 at 62.6% (221 of 353 days).
What does AQI 40 mean for health? ▼
An AQI of 40 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 Williamsport, PA compare to other metro areas? ▼
The Williamsport, PA metro has 77.5% good air days. Similar metros: Altoona, PA (76.9% good), Beaver Dam, WI (72.3% good), Bismarck, ND (76.7% good).
What is the 90th percentile AQI for Williamsport, PA? ▼
The 90th percentile AQI for the Williamsport, PA metro area is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (USG).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Williamsport, PA, 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, Williamsport, PA · 2020–2025