What is the air quality in Cascade County, Montana?

EPA monitors reported only 87 days for Cascade County in 2024, below the 100-day floor used for annual conclusions. Within that limited sample, the median AQI was 46 and 52 days were rated Good; this does not describe the full year.

What is the main pollutant in Cascade County?

The primary pollutant in Cascade County is Fine Particles (PM2.5), which was the main AQI driver on 87 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.

How many unhealthy air days does Cascade County have?

Among 87 reported days in 2024, 0 reached Unhealthy or worse. Because the record is below 100 monitored days, that count cannot establish how many unhealthy days occurred across the full year.

Is the air quality in Cascade County getting better or worse?

Air quality in Cascade County is worsening across floor-qualifying years (2020-2023); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 90.0% (323 of 359 days). Lowest qualifying Good-day share: 2023 at 50.1% (176 of 351 days).

What does AQI 46 mean for health?

The median of the 87 reported days was AQI 46, in the "Good" category. The limited sample is not enough to assign the county a full-year health grade. See the AQI category guide for day-level meaning and EPA AirNow for current conditions.

How does Cascade County compare to other counties in Montana?

Cascade County is not placed in county comparisons because its 87-day record is below the 100-day comparison floor.

What is the 90th percentile AQI in Cascade County?

The 90th percentile AQI for Cascade County is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 74 (Moderate).

Montana · County air quality · 2024

Cascade County, Montana

Limited EPA sample: 87 monitored days, below the 100-day floor for a full-year verdict. The figures below describe only those reported days.

Compiled by PlainAirData · August 23, 2026

46
Sample median AQI: 59.8%
Good in sample: 0
Unhealthy in sample: 87
100-day comparison floor

Cascade County has only 87 EPA-monitored days in 2024, below the 100-day annual floor

According to the U.S. EPA Air Quality System, Cascade County, Montana reported 87 monitored days in 2024. That sample is too thin for a full-year air-quality grade or peer ranking. Use the figures only as the reported-day record, and check AirNow for current conditions.

Data source EPA Air Quality System (AQS)

Monitored days: Cascade County reported 87 monitored days in 2024, below the 100-day floor: sample-only, not a full-year peer rank.
Sample median AQI: Sample median AQI: 46
Annual floor: Annual floor: 100

Cascade County's Good-day share fell from 90.0% to 50.1% between the 2022 and 2023 EPA annual releases, a change of -39.8 percentage points.
Cascade County's median AQI rose from 23 to 50 between the 2022 and 2023 EPA annual releases, a change of +27 points.
Cascade County's peak single-day AQI rose from 128 to 170 between the 2022 and 2023 EPA annual releases, a change of +42 points.
Cascade County's Unhealthy-category days rose from 0 to 1 between the 2022 and 2023 EPA annual releases, a change of +1 days.

Data updated August 2026

Good · 52 d · 59.8%
Moderate · 35 d · 40.2%

How did Cascade County's reported sample break down in 2024?

Across 87 monitored days, 52 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 74 (Moderate).

EPA AQS →

Pollutant Breakdown

Days where each pollutant was the primary driver of AQI readings in Cascade County.

PM2.5 · 87 days · 100.0%

Sample Coverage and Health Context

Limited sample

Cascade County has no annual health grade because only 87 days were reported, below the 100-day floor. The 59.8% Good-day share describes only that sample.

Reported days do not reveal what happened during unmonitored parts of the year, including seasonal smoke, ozone, or inversion periods. Use these values as a description of the available EPA sample only, and check AirNow.gov for current health guidance.

The dominant pollutant is PM2.5, driving AQI on 87 of 87 monitored days.

5-Year Air Quality Trend

Air quality is worsening in Cascade County. Highest Good-day share: 2022 (90.0%, 323 of 359 monitored days). The 2024 row is shown for transparency but excluded from the direction because it has fewer than 100 monitored days.

Year	Good	Moderate	USG	Unhealthy	Median AQI	Max AQI
2020	314	42	3	0	24	115
2021	296	58	9	2	27	160
2022	323	34	2	0	23	128
2023	176	169	5	1	50	170
2024	52	35	0	0	46	74

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Cascade County, Montana · 2020–2025 Accessed 2026-08-23

Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.

Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.