Metro area air quality · 2025

Gillette, WY

Median AQI 44 (Good). 74.3% of monitored days rated Good across this metro's EPA monitoring network.

Compiled by PlainAirData · August 23, 2026

44
Median AQI: 74.3%
Good-air days: 1
Unhealthy days: 54%
Cleaner than US metros

Gillette, WY posted a 2025 median AQI of 44 (Good) with 74.3% Good days

According to the U.S. EPA Air Quality System, the Gillette, WY CBSA recorded a median AQI of 44 across 365 monitored days in 2025, with 74.3% rated Good and 1 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 Gillette, WY CBSA's 74.3% Good-day share places it cleaner than 54% of US metros in 2025.
Closest median-AQI peer: Bartlesville, OK (68.0% Good, median AQI 44) is the closest nationwide median-AQI peer to Gillette, WY.
2020–2025 Good-day shift: Gillette, WY's Good-day share moved +6.4 points from 2020 to 2025 (median AQI +0).
Median AQI: Median AQI: 44

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

The verdict

Gillette, WY's peak reading 156 is in the upper max-AQI tercile among CBSA metros here. On the EPA scale the metro runs good, cleaner than the median US metro, with a median AQI of 44 and 74.3% of 365 monitored days in the Good band.

44
median AQI · Good: 74.3%
days rated Good: 54%
cleaner than US metros: 156
worst single reading

1 day reached Unhealthy or worse across the metro's monitors in 2025.

Gillette, WY metro's Good-day share rose from 63.9% to 74.5% between the 2024 and 2025 EPA annual releases, a change of +10.5 percentage points.
Gillette, WY metro's Unhealthy-category days fell from 2 to 1 between the 2024 and 2025 EPA annual releases, a change of -1 days.

Gillette, WY's peak reading 156 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 156 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 44 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 271 Good (74%), 92 Moderate (25%), and 1 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 62; the highest single-day reading hit 156 (Unhealthy).

Across 2020–2025, Good-day share shifted +6.4 points and median AQI moved +0 (improving). The annual record contains 1 day at Unhealthy or worse. Metros with comparable AQI profiles include Bartlesville, OK (68.0% good, AQI 44); Berlin, NH-VT (81.5% good, AQI 44); Bloomington, IL (66.0% good, AQI 44).

Health effects of air pollution →

Air Quality Summary

Median AQI

Good

Good Days

74.3%

271 of 365 days

Max AQI

156

Unhealthy

Health Grade

Moderate

90th pct: 62

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

271

74%

Moderate

25%

USG

Unhealthy

Very Unhealthy

Hazardous

Health Impact Assessment

Moderate

The Gillette, WY metro area's air quality is rated Moderate based on 74.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 156. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Gillette, WY metro compare?

How Gillette, WY compares

Compare against

Good-day share better than typical

Gillette, WY 74.3%

Bartlesville, OK 68.0%

Typical US metro 70.6%

Median AQI worse than typical

Gillette, WY 44

Bartlesville, OK 44

Typical US metro 41

Unhealthy days / yr about typical

Gillette, WY 1

Bartlesville, OK 1

Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Gillette, WY metro. Highest Good-day share: 2025 (74.5%, 271 of 364 monitored days).

Year	Good	Moderate	Unhealthy	Median AQI	Max AQI
2020	247	116	0	44	124
2021	218	131	0	44	143
2022	210	146	1	48	584
2023	245	113	1	45	177
2024	232	129	2	44	161
2025	271	92	1	44	156

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Gillette, WY (44).

Bartlesville, OK

Median AQI 44 · 68.0% Good-day share

Berlin, NH-VT

Median AQI 44 · 81.5% Good-day share

Bloomington, IL

Median AQI 44 · 66.0% Good-day share

Boston-Cambridge-Newton, MA-NH

Median AQI 44 · 71.0% Good-day share

Bridgeport-Stamford-Norwalk, CT

Median AQI 44 · 64.7% Good-day share

Buffalo-Cheektowaga-Niagara Falls, NY

Median AQI 44 · 63.8% Good-day share

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Gillette, WY's 1 (independent of median AQI).

Ann Arbor, MI

1 unhealthy-or-worse days · median AQI 41

Bangor, ME

1 unhealthy-or-worse days · median AQI 33

Baraboo, WI

1 unhealthy-or-worse days · median AQI 35

Beaumont-Port Arthur, TX

1 unhealthy-or-worse days · median AQI 52

Beaver Dam, WI

1 unhealthy-or-worse days · median AQI 40

Bellingham, WA

1 unhealthy-or-worse days · median AQI 31

Frequently Asked Questions

What is the 90th percentile AQI for Gillette, WY? ▼

The 90th percentile AQI for the Gillette, WY metro area is 62, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 156 (Unhealthy).

How many unhealthy air days does Gillette, WY have? ▼

In 2025, the Gillette, WY metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 156.

What is the air quality in the Gillette, WY metro area? ▼

The Gillette, WY metro area has a median Air Quality Index (AQI) of 44, rated "Good." 74.3% of monitored days (271 out of 365) had good air quality in 2025.

Is air quality in Gillette, WY getting better or worse? ▼

Air quality in the Gillette, WY 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 74.5% (271 of 364 days). Lowest qualifying Good-day share: 2022 at 58.8% (210 of 357 days).

What does AQI 44 mean for health? ▼

An AQI of 44 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 Gillette, WY compare to other metro areas? ▼

The Gillette, WY metro has 74.3% good air days. Similar metros: Bartlesville, OK (68.0% good), Berlin, NH-VT (81.5% good), Bloomington, IL (66.0% good).

Data Sources

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