# Missoula, MT Air Quality Index (AQI) Today > Source: https://breathecheck.com/air-quality/us/montana/missoula/ > Live AQI for Missoula, MT with a plain verdict — go, short and unloaded, or don't go — plus the monitor behind it and our own hourly record. # Missoula, MT Air Quality Index (AQI) Today By BreatheCheck Editorial — no named author, deliberately. Why a verifiable pipeline beats a byline → Right now: Missoula is at 13 , good. ## Is the air safe to breathe in Missoula today? Go Normal outdoor plans. No change needed. Short & unloaded A 20-minute dog walk, not a 2.5-hour run. Keep it brief and easy. Don’t go Move it indoors. Above 200 that becomes everyone, not just sensitive groups. Above 200 this stops being a personal call: everyone indoors. Duration and intensity are two separate dials | Under 20 min | 20–60 min | Over an hour | | Easy | Go | Go | Go | | Moderate | Go | Go | Go | | Hard | Go | Go | Go | Where people actually draw the line **All the thresholds people reported, and who reported them** - 60 Asthmatic runner one runner’s own 156-run log - 75–100 Daycare / school parents and staff in one r/toddlers thread, Aug 2025 — not a published rule - 100 Parent community-reported, escalating at 150 and 200 - 110 Runner community-reported EPA classifies 101–150 as Unhealthy for Sensitive Groups. That is an attributed classification, not a verdict on your lungs specifically. If you’re staying in, filter the room you’re actually in A portable HEPA unit or a Corsi-Rosenthal box — one builder put theirs at about $130 for a 12×14 bedroom. We don’t default to a MERV-13 swap in whole-house HVAC: it can restrict airflow, and the safe version needs a static-pressure check first. Dominant pollutant O3 UV index — modelled UV hour by hour in Missoula → Forecast — pipeline ### One drain, and rules written for smoke Missoula’s air problem is its floor plan. The city occupies a valley near 3,200 feet where the Clark Fork comes out of Hellgate Canyon and the Bitterroot joins from the south, with mountains on every side. On a cold, still night the dense air at the bottom has nowhere to go, and whatever is emitted into it stays there until the weather pattern changes. That has been understood here for a long time. By 1969, with a pulp mill and log yards then working the valley, Life reported residents driving with headlights on in daylight. The mills and most of the yards went; what remained as the cold-season source was residential wood burning, and research across western Montana valley communities has attributed the majority of their wintertime fine particulate to wood smoke. Missoula’s answer was an air stagnation zone covering the valley floor and ground beyond the city limits. No wood stove has been legally installed inside it since 1994 — pellet and gas appliances only — and an uncertified device must come out when a property changes hands, with a certificate of compliance filed at the county before the sale can close. Summer runs the same trap on a different fuel, regional wildfire smoke settling in and not scouring out overnight. Mount Sentinel and Mount Jumbo rise more than 1,500 feet straight off the valley floor at the east end of town, so on an inversion morning the top of the haze is somewhere on those slopes. The monitor is on the floor, which is where people live. ## Where this number sits Of the 121 US metros reporting to us right now, Missoula is number 118 and number 2 of the 2 we track in Montana. The pollutant driving it today is O3. Nearby metros we also measure, and what they read at the same hour: - Spokane, WA — 170 miles away, AQI 63 - Boise, ID — 249 miles away, AQI 52 - Idaho Falls, ID — 254 miles away, AQI 7 - Billings, MT — 273 miles away, AQI 43 Why a metro a short drive away reads differently → Where this reading comes from Missoula, with 38 nearby sensors. Local sensors around Missoula median 19 at the same hour — a 6-point higher read than the monitor. The gap, across every metro → ## Our history for Missoula so far Daily maximum, our own readings. 2 days since 2026-08-16; nothing back-filled. Why we keep our own → 0 of the 2days we have recorded so far went above AQI 100. ## Questions about Missoula **What is the air quality in Missoula right now?** AQI 13 — Good. That is number 118 of the 121 US metros reporting to us at this hour. **Which monitor does this number come from?** Missoula. Local sensors median 19 at the same hour, a 6-point difference. One instrument reports for the whole metro, so the side farthest from it is the least well described. **How does Missoula compare with metros nearby?** At this hour: Spokane 63, Boise 52, Idaho Falls 7, Billings 43. A gap that size over that distance usually means different terrain, traffic or wind rather than a broken sensor. **Does this include pollen?** No. The AQI covers PM2.5, PM10, ozone, NO₂, SO₂ and CO. A high-pollen day can read clean here and still put someone in bed. What the number means, band by band → · UV in Missoula → · Why apps disagree → ## Put this number in context On this page Alert me when Missoula turns One email when it crosses your threshold. Updated 17 Aug 2026, 11:49 UTC