Metro area air quality · 2024

Hilo, HI

Median AQI 21 (Good). 97.0% of monitored days rated Good across this metro's EPA monitoring network.

21
Median AQI
97.0%
Good-air days
0
Unhealthy days
95%
Cleaner than US metros

Aggregated from EPA Air Quality System (2024), 366 monitored days. EPA AQS → · NOAA →

Insights: Hilo, HI metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 21 over 366 measured days in 2024, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 355 Good days (97%), 11 Moderate (3%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 33 while the highest single-day reading hit 75 (Moderate). Metro residents averaged roughly 29.1 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by +3 and the median AQI moved -2 points, which classifies the multi-year trajectory as stable. The metro avoided any Unhealthy-tier days entirely, an outcome that typically reflects favorable wind patterns, lower industrial density, or effective regional emission controls. Metros with comparable AQI profiles include Kahului-Wailuku-Lahaina, HI (99.7% good, AQI 21); Shelton, WA (93.2% good, AQI 21); Aberdeen, WA (96.5% good, AQI 20).

Air Quality Summary

Median AQI

21

Good

Good Days

97.0%

355 of 366 days

Max AQI

75

Moderate

Health Grade

Excellent

90th pct: 33

AQI Day Breakdown (2024)

Distribution of 366 monitored days across EPA AQI categories.

Good

355

97%

Moderate

11

3%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Excellent

The Hilo, HI metro area's air quality is rated Excellent based on 97.0% good air days. No unhealthy air days were recorded in 2024.

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

How does the Hilo, HI metro compare?

How Hilo, HI compares

Good-day share better than US avg
Hilo, HI 97.0%
Kahului-Wailuku-Lahaina, HI 99.7%
US average 70.2%
Median AQI better than US avg
Hilo, HI 21
Kahului-Wailuku-Lahaina, HI 21
US average 41
Unhealthy days / yr better than US avg
Hilo, HI 0
Kahului-Wailuku-Lahaina, HI 0
US average 1

5-Year Air Quality Trend

Air quality is stable in the Hilo, HI metro. Best year: 2024 (355 good days).

Year Good Moderate Unhealthy Median AQI
2020 352 14 0 23
2021 336 29 0 27
2022 328 37 0 33
2023 336 29 0 23
2024 355 11 0 21

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Hilo, HI.

Kahului-Wailuku-Lahaina, HI

AQI 21 · 99.7% good

21

Shelton, WA

AQI 21 · 93.2% good

21

Aberdeen, WA

AQI 20 · 96.5% good

20

Centralia, WA

AQI 22 · 93.3% good

22

Gardnerville Ranchos, NV

AQI 22 · 90.1% good

22

Longview, WA

AQI 22 · 95.4% good

22

More Air Quality Data

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Air Quality Guides

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Understanding AQI

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Health Effects of Air Pollution

How PM2.5 and ozone exposure affects respiratory and cardiovascular health.

Frequently Asked Questions

What is the air quality in the Hilo, HI metro area? ▼
The Hilo, HI metro area has a median Air Quality Index (AQI) of 21, rated "Good." 97.0% of monitored days (355 out of 366) had good air quality in 2024.
How many unhealthy air days does Hilo, HI have? ▼
In 2024, the Hilo, HI metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 75.
Is air quality in Hilo, HI getting better or worse? ▼
Air quality in the Hilo, HI metro is stable based on 5-year trends (2020-2024). Best year: 2024 with 355 good days. Worst year: 2022 with 328 good days.
What does AQI 21 mean for health? ▼
An AQI of 21 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
What is the 90th percentile AQI for Hilo, HI? ▼
The 90th percentile AQI for the Hilo, HI metro area is 33, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 75 (Moderate).
How does Hilo, HI compare to other metro areas? ▼
The Hilo, HI metro has 97.0% good air days. Similar metros: Kahului-Wailuku-Lahaina, HI (99.7% good), Shelton, WA (93.2% good), Aberdeen, WA (96.5% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2024. The AQS collects ambient air monitoring data from state, local, and tribal monitoring agencies across the United States.

Metrics: Air Quality Index (AQI) is calculated using EPA-standard breakpoints for six criteria pollutants: PM2.5, PM10, Ozone, NO2, CO, and SO2. Median AQI, max AQI, and 90th percentile AQI are computed from daily measurements. Good days percentage reflects days with AQI 0–50.

Coverage: 501 metro areas (Core Based Statistical Areas). Only metros with active monitoring stations are included. Unmonitored areas are not represented.

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

Source: U.S. EPA, AirNow / AQS Air Quality Index readings and pollutant concentrations · 2025