Metro area air quality · 2025

Truckee-Grass Valley, CA

Median AQI 42 (Good). 79.8% of monitored days rated Good across this metro's EPA monitoring network.

42
Median AQI
79.8%
Good-air days
0
Unhealthy days
67%
Cleaner than US metros

Truckee-Grass Valley, CA posted a 2025 median AQI of 42 (Good) with 79.8% Good days

According to the U.S. EPA Air Quality System, the Truckee-Grass Valley, CA CBSA recorded a median AQI of 42 across 362 monitored days in 2025, with 79.8% 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 Truckee-Grass Valley, CA CBSA's 79.8% Good-day share places it cleaner than 67% of US metros in 2025.
Closest median-AQI peer
Allentown-Bethlehem-Easton, PA-NJ (66.8% Good, median AQI 42) is the closest nationwide median-AQI peer to Truckee-Grass Valley, CA.
2020–2025 Good-day shift
Truckee-Grass Valley, CA's Good-day share moved +15.4 points from 2020 to 2025 (median AQI -4).
Median AQI
Median AQI: 42

Aggregated from EPA Air Quality System (2025), 362 monitored days. EPA AQS →

The verdict

Truckee-Grass Valley, CA's Good-day share (79.8%) 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 42 and 79.8% of 362 monitored days in the Good band.

42
median AQI · Good
79.8%
days rated Good
67%
cleaner than US metros
108
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
  • Truckee-Grass Valley, CA metro's Good-day share fell from 86.2% to 80.1% between the 2024 and 2025 EPA annual releases, a change of -6.2 percentage points.
  • Truckee-Grass Valley, CA metro's peak single-day AQI fell from 132 to 108 between the 2024 and 2025 EPA annual releases, a change of -24 points.
  • Truckee-Grass Valley, CA metro's median AQI rose from 36 to 42 between the 2024 and 2025 EPA annual releases, a change of +6 points.

Compared against 363 monitored days in 2024 and 361 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

Truckee-Grass Valley, CA's Good-day share (79.8%) sits in the middle CBSA tercile on this extract. Signature read: 79.8% 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 42 over 362 measured days in 2025 (Good / Good). The monitored-day split lands at 289 Good (80%), 72 Moderate (20%), and 1 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 58; the highest single-day reading hit 108 (USG).

Across 2020–2025, Good-day share shifted +15.4 points and median AQI moved -4 (improving). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Allentown-Bethlehem-Easton, PA-NJ (66.8% good, AQI 42); Amarillo, TX (78.4% good, AQI 42); Carson City, NV (86.2% good, AQI 42).

Understanding AQI →

Air Quality Summary

Median AQI

42

Good

Good Days

79.8%

289 of 362 days

Max AQI

108

USG

Health Grade

Good

90th pct: 58

AQI Day Breakdown (2025)

Distribution of 362 monitored days across EPA AQI categories.

Good

289

80%

Moderate

72

20%

USG

1

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Truckee-Grass Valley, CA metro area's air quality is rated Good based on 79.8% 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 Truckee-Grass Valley, CA metro compare?

How Truckee-Grass Valley, CA compares

Good-day share better than typical
Truckee-Grass Valley, CA 79.8%
Allentown-Bethlehem-Easton, PA-NJ 66.8%
Typical US metro 70.6%
Median AQI worse than typical
Truckee-Grass Valley, CA 42
Allentown-Bethlehem-Easton, PA-NJ 42
Typical US metro 41
Unhealthy days / yr better than typical
Truckee-Grass Valley, CA 0
Allentown-Bethlehem-Easton, PA-NJ 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Truckee-Grass Valley, CA metro. Highest Good-day share: 2024 (86.2%, 313 of 363 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 223 111 11 46
2021 183 129 13 50
2022 185 161 3 50
2023 282 81 0 42
2024 313 50 0 36
2025 289 72 0 42

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Truckee-Grass Valley, CA (42).

Allentown-Bethlehem-Easton, PA-NJ

Median AQI 42 · 66.8% Good-day share

42

Amarillo, TX

Median AQI 42 · 78.4% Good-day share

42

Carson City, NV

Median AQI 42 · 86.2% Good-day share

42

Casper, WY

Median AQI 42 · 86.3% Good-day share

42

Clarksville, TN-KY

Median AQI 42 · 72.0% Good-day share

42

Daphne-Fairhope-Foley, AL

Median AQI 42 · 75.5% Good-day share

42

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Truckee-Grass Valley, CA'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 Truckee-Grass Valley, CA have? ▼
In 2025, the Truckee-Grass Valley, CA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 108.
What is the air quality in the Truckee-Grass Valley, CA metro area? ▼
The Truckee-Grass Valley, CA metro area has a median Air Quality Index (AQI) of 42, rated "Good." 79.8% of monitored days (289 out of 362) had good air quality in 2025.
Is air quality in Truckee-Grass Valley, CA getting better or worse? ▼
Air quality in the Truckee-Grass Valley, CA 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: 2024 at 86.2% (313 of 363 days). Lowest qualifying Good-day share: 2022 at 53.0% (185 of 349 days).
What does AQI 42 mean for health? ▼
An AQI of 42 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 Truckee-Grass Valley, CA compare to other metro areas? ▼
The Truckee-Grass Valley, CA metro has 79.8% good air days. Similar metros: Allentown-Bethlehem-Easton, PA-NJ (66.8% good), Amarillo, TX (78.4% good), Carson City, NV (86.2% good).
What is the 90th percentile AQI for Truckee-Grass Valley, CA? ▼
The 90th percentile AQI for the Truckee-Grass Valley, CA metro area is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 108 (USG).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Truckee-Grass Valley, CA, 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, Truckee-Grass Valley, CA · 2020–2025