Westminster Real-Time AQI Tracker
Get Alerts For Unhealthy AQI In Your Area
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.
What's Actually In Westminster Air Today?
What High AQI Means for Your Lungs in Westminster
How to Read AQI
The Air Quality Index (AQI) measures how polluted the air is and how it may affect your health.
0–50 (Good): Air quality is satisfactory.
51–100 (Moderate): Acceptable, but some pollutants may pose minor concerns.
101–150 (Unhealthy for Sensitive Groups)
151–200 (Unhealthy)
201–300 (Very Unhealthy)
301+ (Hazardous)
Moderate
Still okay for most, but if you have asthma or allergies, take it easy and avoid long outdoor workouts.
Shop MERV 11 filters→What's the Right Filter for Your AQI Level?
Check Today's Live Real Time Air Quality Index AQI Map in Westminster, CO Now
TL;DR
The live map above shows Westminster’s current Air Quality Index (AQI) and the pollutant behind it. In Westminster, Colorado, a Denver suburb in Adams and Jefferson counties, summer ozone is a timing problem you plan around. Smoke and winter inversions bring fine particles (PM2.5), a filtration problem: at AQI 100, Filterbuy recommends MERV 13, fan On, a portable HEPA cleaner in each occupied room, and a closed-up house.
Key Takeaways
Ozone drives most high AQI days from mid-May to mid-September; PM2.5 drives smoke and inversion days.
Westminster straddles the Denver metro’s two worst-graded counties in the American Lung Association’s 2026 report: Jefferson (ozone) and Adams (particle spikes).
MERV 13 is Filterbuy’s smoke tier, and AQI 100 is its action line. Pleated filters don’t capture ozone or other gases.
How to Read Westminster’s Live AQI Map
The AQI is EPA’s 0-to-500 scale. Filterbuy reads Westminster’s map in this order:
Pollutant first. Ozone or PM2.5 sets the playbook.
Color second. The color tells you who needs to adjust.
Number and timestamp last. They show how near the next category is.
Is Westminster’s Air Safe to Breathe Right Now? What Each AQI Color Means
It depends on the map’s color. Orange is where children, older adults, and anyone with asthma or heart or lung disease should start to ease up. The categories are EPA’s, from AirNow.
Why Westminster’s AQI Can Lag Behind What You See or Feel
Real-time readings use EPA’s NowCast calculation, which blends several hours of data, so fast-moving smoke can outrun the number by an hour or two. Filterbuy’s rule: if it smells smoky, act as if the AQI is higher.
For local detail, see the West 72nd Avenue air sensor listed on AQICN; for the bigger picture, the Colorado statewide live AQI map or Denver live AQI map.
Where to Check Westminster’s Air Quality Forecast and Alerts
CDPHE posts the Front Range forecast daily at 4 p.m. on its Front Range air quality advisory page. Summer alerts cover western Adams and Jefferson counties, home to Westminster, and the city runs its own Westminster air quality and ozone alert sign-ups.
Ozone Action Day Alert: ozone may reach Unhealthy for Sensitive Groups; plan hard exercise before noon.
Action Day for Multiple Pollutants: ozone and fine particles are both high, often from smoke.
Winter Action Days (Oct. 31–Mar. 31): inversions trap pollution, and Westminster bars wood-burning stoves.
What’s in Westminster’s Air: Ozone, PM2.5, and Their Sources
Ground-level ozone is Westminster’s main air quality problem. It forms when nitrogen oxides and volatile organic compounds, mostly from traffic and oil and gas operations, bake in strong sunlight, and Front Range terrain keeps them from clearing out.
PM2.5 comes second, from wildfire smoke, wood stoves, and diesel exhaust that winter inversions hold close to the ground.
How Westminster’s Air Compares with Other U.S. Cities
The American Lung Association’s 2026 “State of the Air” Colorado release ranked the metro 8th worst in the nation for ozone. Westminster sits in both of its worst-graded counties:
Jefferson County: 29.7 unhealthy ozone days per year (2022–2024), an F grade and the metro’s worst.
Adams County: 1.7 unhealthy short-term particle days per year, a C grade and the metro’s worst for particle spikes.
Ozone also swings sharply year to year, as Regional Air Quality Council (RAQC) counts for the nine-county region show (via Denver Post coverage of the 2026 ozone season, ):
Filterbuy’s read: heat drives these swings as much as smoke. RAQC’s director said 2026 was too high even without smoke days.
Wildfire Smoke and Winter Inversions: Westminster’s Episodic Air Quality Risks
Westminster’s sharpest AQI jumps come from wildfire smoke and winter inversions, the source of the metro’s “brown cloud.”
On December 30, 2021, the Marshall Fire destroyed 1,084 homes in Louisville, Superior, and unincorporated Boulder County, just northwest of Westminster along US 36 (Colorado Newsline’s Marshall Fire damage tally).
What a Westminster Air Quality Alert Means for Your Day
On an Ozone Action Day, get outside in the morning, since ozone peaks in mid-afternoon. Westminster also suggests mowing after 5 p.m. and has a Mow Down Pollution rebate for electric mowers.
On a smoke or PM2.5 Action Day, check AirNow and CDPHE’s guidance first, then follow Filterbuy’s AQI 100 steps below. If you have asthma or a heart or lung condition, follow your doctor’s advice.
Filterbuy’s Take: What Westminster’s AQI Means Inside Your Home
Filterbuy manufactures HVAC filters, so here’s the honest part first: a filter captures particles, not ozone.
An ozone day is a timing problem. Filters can’t catch ozone gas, but it breaks down fairly quickly indoors, so close up during the afternoon peak.
A smoke or inversion day is a filtration problem. Fine particles linger until a filter captures them, so use the AQI 100 steps below.
Filterbuy’s Colorado statewide live AQI map page reports that filters pulled from Front Range homes during the 2020 wildfire season came out visibly darker within two weeks. During smoke, replace yours when it looks dark brown or black, and keep spares.
Most people don’t want a lecture on filtration. They want to know whether the filter in the hallway closet is the right one, and whether it can stay another month.
Michelle Wan, Brand Manager and Air Quality Writer, Filterbuy
Filterbuy’s Westminster Filter Calendar
Mid-May: fresh filter before ozone season.
Late summer: keep a spare MERV 13 on hand for fire-season smoke.
Before November 1: fresh filter before winter inversion season.
A Filterbuy air filter subscription can ship filters every 30, 60, or 90 days.
Which Air Filter Westminster’s AQI Calls For: Filterbuy’s AQI 100 Action Line
At AQI 100 and above, Filterbuy recommends four steps for smoke and fine particles: put a MERV 13 filter in your HVAC system, set the thermostat fan to On so it filters continuously, run a portable HEPA air cleaner in each occupied room (bedrooms first), and close the house up. Closing up means windows and doors shut and no candles, frying, smoking, or vacuuming without a sealed HEPA vacuum while smoke is in. AQI 100 is Filterbuy’s action line, not a category change. On EPA’s scale, orange starts at 101.
EPA recommends a filter rated MERV 13 or higher in central HVAC systems during smoke events (EPA wildfire and indoor air quality guidance). EPA also notes that most furnaces and HVAC systems can accommodate MERV 13 without equipment problems, provided the filter is replaced frequently (EPA Guide to Air Cleaners in the Home). The only check is fit, and the mistake we see most often is the wrong size. Filterbuy makes 600+ sizes plus custom cuts, and we trim each filter a half inch under the nominal size so it slides in without binding. “I don’t want anyone to feel like they need an HVAC license just to pick the right filter,” says Michelle Wan, Filterbuy’s Brand Manager and Air Quality Writer.
Find your size on the air filter size chart, then shop MERV 13 air filters in that size. See our best MERV filter for wildfire smoke guide for the seasonal swap.
What If Your Westminster Home Has No Central HVAC?
Without ducts, portable HEPA air cleaners are your primary defense, not an extra. EPA’s cleaner air room guidance says to choose one whose smoke CADR (clean air delivery rate) is at least two-thirds of the room’s square footage, so a 300-square-foot bedroom needs a smoke CADR of about 200. EPA advises against ozone-producing cleaners, so pick a CARB-certified unit and run it on high.
A DIY box-fan cleaner with MERV 13 filters is a reasonable stopgap, not a replacement for a certified cleaner. EPA advises a UL- or ETL-listed fan made since 2012, and never leaving an older fan running unattended.
Swamp coolers pull outdoor air inside, so EPA suggests covering their intakes with MERV 13 filters if you can reach them safely, or using them sparingly during smoke.
Supporting Statistics Behind This Westminster Air Quality Guide
Americans spend about 90% of their time indoors, where some pollutants run 2 to 5 times higher.
Why it matters: on smoky days, indoor air is what you breathe.
Source: U.S. EPA, Report on the Environment: Indoor Air Quality
Home HVAC systems usually run less than 25% of the time in season.
Why it matters: filters only work while the blower runs, hence fan On.
985,296 Colorado children breathe unhealthy levels of air pollution.
Westminster Air Quality FAQs
What is the air quality in Westminster today?
The live map at the top of this page shows today’s AQI and main pollutant.
Is the air quality bad in Westminster today?
It’s bad for sensitive groups at orange (101+) and for everyone at red (151+).
What is Westminster’s PM2.5 today?
The live map shows PM2.5 whenever fine particles are the main pollutant, usually from wildfire smoke or a winter inversion. At AQI 100 and above, follow Filterbuy’s four steps: MERV 13 in the HVAC, fan On, a portable HEPA cleaner in each occupied room, and the house closed up.
What MERV rating do I need for wildfire smoke in Westminster?
MERV 13, in your exact filter size. It’s the tier Filterbuy recommends for smoke, and EPA recommends MERV 13 or higher in central HVAC systems during smoke events.
When should I change my air filter during wildfire smoke?
Check it during a smoke event and replace it when it looks dark brown or black, even if that’s well before its normal interval. Keep a spare on hand.
Westminster Air Quality Glossary
Air Quality Index (AQI): EPA’s 0–500 scale with six color-coded health categories.
PM2.5: Fine particles 2.5 micrometers or smaller.
CADR: Clean air delivery rate of a portable cleaner.
Ground-level ozone: A gas formed when emissions react in sunlight.
NowCast: EPA’s real-time AQI method.
Temperature inversion: Warm air trapping cold, polluted air near the ground.
Action Day: A CDPHE alert for unhealthy air.
CDPHE: Colorado Department of Public Health and Environment.
MERV: Minimum Efficiency Reporting Value, a 1–16 filter efficiency rating.
HEPA: High-efficiency particulate air filtration, used in portable air cleaners, never in HVAC filter slots.