# Montana air quality today — live AQI by metro > Source: https://breathecheck.com/air-quality/us/montana/ > Live AQI for 2 Montana metros, updated hourly from EPA AirNow. Where the state's air is worst right now, and how far apart its cities are. # Montana air quality today Updated 14 Sep 2026, 22:12 UTC · LIVE 2 metros tracked Across the 2 Montana metros BreatheCheck measures, air is worst right now in Billings at AQI 52 (Moderate) and cleanest in Missoula at AQI 21 . That is a 31 -point spread inside one state — a state-level number would hide it, which is why this page does not publish one. ## Which Montana city has the worst air quality right now? | # | Metro | AQI | UV now | Dominant | | 1 | Billings no page yet | 52 Moderate | 2.3 | PM2.5 | | 2 | Missoula | 21 Good | 1.7 | O3 | ## What is the UV index in Montana today? The strongest UV in Montana today is 5.6 (High) in Billings, arriving around 1pm local time. The mildest of the 2 metros we model here peaks at 3.5 in Missoula. UV is modelled, not measured — unlike the AQI above it, which comes off an instrument. Hour by hour in Missoula → ## Cold air pooling in a narrow mountain valley Montana’s air problems are the size of a valley rather than the size of the state. West of the Continental Divide the terrain is a series of narrow intermountain basins — Missoula, the Flathead, the Kootenai at Libby among them — and on a cold, clear, windless winter night each one settles its own layer of dense air under a lid that holds until the sun breaks it. Whatever burns locally stays underneath. Libby, a town of a few thousand, was designated nonattainment for fine particulate on exactly that mechanism, and the source apportionment there left little room for argument. Chemical mass balance modeling of the winter of 2003–2004 put residential wood combustion at an average 82 percent of the fine particles collected on the filters. Nearly 1,200 old stoves were then changed out for cleaner models between 2005 and 2007, and a follow-up study measured average winter PM2.5 down about 20 percent, with the woodsmoke fraction down about 28 percent, against that pre-changeout winter. EPA redesignated Libby to attainment in 2023, and it now runs under a limited maintenance plan. Late summer works the same trap on different fuel. Smoke from fires inside the state and from farther west settles into those same basins and is slow to leave, so the year carries two separate particulate seasons with a quieter stretch between them. Montana DEQ updates its monitoring network hourly under the name Today’s Air, and it splits the open burning year by season: counties regulate burning in spring and summer, DEQ issues county-wide restrictions in fall off the dispersion forecast, and winter burning is granted case by case. ## Where do these Montana readings come from? 2 of the 2 metros here report from a named regulatory monitor — Billings, Missoula. The dominant pollutant across Montana today is PM2.5 in some metros, O3 in others. We track 2 metropolitan areas in Montana, not the whole state, and 1 of them has a page of its own. There is no state-wide average here on purpose: averaging 2 metros into one figure would invent a value for all the ground between them. How we measure, and what we refuse to estimate → ## Neighbouring states Smoke and inversions do not stop at a state line, so when Montana looks wrong the answer is often next door. ## Related Updated 14 Sep 2026, 22:12 UTC