Air quality index (AQI⁺) and PM2.5 air pollution in Montana •
When air quality in your area reaches unhealthy levels, we'll send you a quick alert, along with expert tips on how to reduce your exposure.
Real-time most polluted cities in Montana
Real-time cleanest cities in Montana
When outdoor air quality drops, the EPA recommends upgrading to a MERV 13 filter — or the highest-rated filter your HVAC system can handle — to help capture more of the fine particulate (PM2.5) that comes with poor air quality. MERV 13 is the highest rating most residential systems can run without restricting airflow.
AQI stands for Air Quality Index, the EPA's scale for reporting daily air quality. It runs from 0 to 500. The higher the number, the greater the level of air pollution. Values at or below 100 are generally considered satisfactory; values above 100 mean air quality is unhealthy, first for sensitive groups, then for everyone as numbers climb.
The AQI tracks five major pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. The reported AQI value reflects whichever pollutant is highest at that time — most often ozone or fine particles (PM2.5).
Monitoring stations measure pollutant concentrations, and the EPA converts each into a standardized 0–500 score using set breakpoints. Each pollutant gets its own sub-index, and the highest sub-index becomes the reported AQI. That's why a single number can represent different pollutants on different days.
An AQI of 0–50 is rated "Good" — air quality poses little or no risk. 51–100 is "Moderate," acceptable for most people though unusually sensitive individuals may want to limit prolonged outdoor exertion. Anything at or below 100 is generally considered satisfactory air quality.
100 is the dividing line: at or below it, air quality is satisfactory for the general public. From 101–150, air is "Unhealthy for Sensitive Groups" — people with respiratory conditions, older adults, and children. From 151–200, it's "Unhealthy" and everyone may begin to feel effects.
Short-term AQI spikes usually come from wildfire smoke, temperature inversions that trap pollutants near the ground, high-ozone weather (hot, sunny, stagnant days), or heavy traffic and industrial activity. Check a real-time source like the map on this page to see which pollutant is driving today's reading in your area.
Many runners follow the EPA category lines: below 50, no adjustment needed; 51–100, unusually sensitive people may shorten intense workouts; above 100, sensitive groups are advised to reduce prolonged or heavy outdoor exertion; above 150, that advice extends to everyone. Exercise increases how much air you breathe in, which is why thresholds matter more during workouts.
A common rule of thumb is to keep windows open when the AQI is under 100 and close them when it climbs above, especially during wildfire smoke events when fine particles are elevated. When windows are closed, running your HVAC system with a fresh filter helps capture particles circulating indoors.
Public health agencies generally suggest considering a well-fitted N95-style respirator outdoors when the AQI exceeds 150, particularly during smoke events. Cloth and surgical masks don't filter fine particles effectively. Follow guidance from your local health department, which may adjust recommendations during severe episodes.
Use the live AQI map to see outdoor air conditions in your part of Montana. The map shows one reading with a matching color for your area so you can plan time outside and focus on indoor air when needed.
Current Status: Montana's real-time AQI level is approximately 30 (Good), indicating air quality is satisfactory for most individuals.
Best Live AQI Maps for Montana:
AirNow.gov/state/montana — Official EPA real-time monitoring
Montana DEQ Today's Air — State-run monitoring with PM2.5 focus
MontanaWildfireSmoke.org — Essential during fire season
aqicn.org/map/montana — Interactive visual map
AQI Scale Quick Reference: 0–50 is Good (ideal conditions, enjoy outdoor activities), 51–100 is Moderate (sensitive groups may experience minor symptoms), 101–150 is Unhealthy for Sensitive Groups (reduce outdoor time if experiencing symptoms), and 151+ is Unhealthy to Hazardous (everyone should limit exposure).
Seasonal Note: Montana's primary air quality concern is particulate matter (PM2.5), particularly during wildfire season. Montana DEQ Understanding the air outside and your potential health risks is critical—wildfire smoke can significantly impact conditions statewide.
Montana’s AQI map shows current outdoor air for your neighborhood so you can time outdoor plans.
Smoke, winter inversions, dust, and traffic are the main drivers of higher readings in the state.
Close windows, use recirculation, and keep at least one room cleaner on bad air days.
Use a Filterbuy MERV 8, 11, or 13 filter that fits your system to help reduce indoor particles while outdoor levels change.
Montana’s air changes with season and location. Summer and early fall can bring wildfire smoke from in-state or regional fires. Winter often has cold, calm periods that hold wood-smoke and other emissions in valleys. Busy road corridors, prescribed burns, and windy days that lift dust in open country can also raise readings. These patterns explain why a valley town and a nearby ridge can look different on the same day.
Wildfire smoke is a leading reason Montana’s air has worsened in recent years. Missoula was flagged for frequent short-term particle spikes, and several urban counties received failing grades for particle pollution. Residents are urged to watch the AQI and reduce outdoor activity when levels rise.
Open the map and check the reading for your town or ZIP code. Lower readings and cooler colors mean cleaner air. Higher readings and warmer colors mean more pollution. If the number rises during the day, keep outdoor time shorter or move hard activity indoors. This matters most for people with asthma, COPD, or heart disease, and for young children and older adults. Conditions can differ between valleys and higher elevations, so it helps to compare nearby areas too.
Use the map the way you use a weather app. Check in the morning before yard work, a run, or kids’ practices. Recheck later if wind shifts, temperatures rise, or smoke appears in the forecast. If your route shows higher readings than your neighborhood, choose a different path or wait until conditions ease.
Keep hard exercise shorter and choose routes away from heavy traffic. Take more breaks, drink water, and rest in shade or an indoor space when you can. If coughing, chest tightness, or shortness of breath starts, move activity indoors and rest.
Keep windows and exterior doors closed during the worst hours. Run AC or HVAC on a “recirculate” setting rather than pulling in outdoor air. Avoid added indoor smoke and strong fumes. Do not smoke indoors. Skip wood fires. Go easy on heavy sprays. If available, run a portable air cleaner in the bedroom or main living area so at least one room stays cleaner.
Keep spare HVAC filters on hand and know the highest MERV your system allows
Pick one cleaner room and be ready to run a portable air cleaner there
Learn recirculate settings on your home system and in your car
Watch wind and smoke forecasts along with the live AQI map
Plan safe cooling options if closing windows could make the home too warm
When air improves, a short cleanup helps lower indoor particles faster. Wipe hard surfaces with a damp cloth or microfiber. Vacuum rugs and carpets with a HEPA-type vacuum if you have one. Wash bedding and throw blankets. Let the HVAC fan run for a few hours with a clean filter, then check the filter and replace it if it looks loaded.
Choose MERV 8 for everyday dust and larger pollen and to help keep the system cleaner.
Use MERV 11 if you have pets or mild allergies and want better capture of small particles like dander and many mold spores.
Consider MERV 13 for finer particles in smoke and urban haze, but only if your system is rated for higher efficiency. If you are not sure, follow the HVAC manufacturer’s guidance or ask a technician.
Filterbuy provides U.S.-made pleated filters in many standard and custom sizes so the filter fits well and reduces air bypass. The synthetic media captures more than basic fiberglass and still supports airflow when changed on time. Many homes replace filters every one to three months. Orders ship fast with free shipping in the continental United States, and Auto-Delivery helps you stay on schedule.
A live map that shows current outdoor air for your location using one number and a matching color.
Check in the morning before outdoor plans. Recheck later if wind shifts, heat builds, or smoke is in the forecast.
Wildfire smoke, wind, valley inversions, and cold or hot spells can change conditions within hours.
Keep sessions shorter or move hard workouts indoors. Sensitive groups should be extra careful.
Keep them closed during the worst hours and use recirculate on AC or HVAC.
A well-fitting N95 or similar respirator can reduce smoke particles. Cloth and surgical masks are not designed for smoke.
Start with MERV 8 for basic dust. Use MERV 11 for homes with pets or mild allergies. Choose MERV 13 for finer particles like smoke only if your system allows it.
Many homes replace filters every 1–3 months. Check sooner during long heating or cooling periods or during smoke events.
Yes. Run it in the bedroom or main living area and follow the maker’s guidance for filter changes.
Stop, go indoors, rest, and follow your care plan. Seek medical advice if symptoms persist or worsen.
