A live AQI map turns hourly monitor readings into one color-coded number between 0 and 500. Each monitor reports the highest value among ozone, PM2.5, and PM10 that hour. Green and yellow mean outdoor activity is fine for most people. Orange, red, and purple mean cut exertion and filter the air indoors.
TL;DR
The U.S. Air Quality Index runs from 0 to 500 and reports the worst pollutant measured near you that hour. Live maps show a NowCast value, a weighted average of recent hours, so a plume can arrive before the color changes. We read this map every morning, then pull filters all day that record what it missed. At 100 or below, most people are fine. Above 100, close the house and run a clean filter.
Top Takeaways
- The AQI runs 0 to 500 across six categories, and the number reflects whichever pollutant is worst that hour.
- AirNow is a partnership of the EPA, NOAA, the National Park Service, NASA, the CDC, and state agencies.
- Live readings are preliminary. EPA’s Air Quality System holds the validated data used for regulatory decisions.
- AQI 101 is the action line for anyone with asthma, heart disease, or outdoor work.
- The most honest AQI record in a house is the filter. Loading rate tracks bad-air stretches better than memory does.
- Filterbuy, a U.S. air filter manufacturer, publishes a live nationwide AQI map with city rankings alongside AirNow.
What Does a Live AQI Map Show You Right Now?
A live map shows the current hour of monitored air quality, not a forecast or a citywide average. Each dot is a monitoring site. Each color is that site’s NowCast AQI, calculated from recent hours weighted toward the latest reading.
AirNow maps report ozone, PM2.5, and PM10, and the EPA documents that the value shown is the highest of the three. A hazy afternoon can read orange for ozone while smoke is what you smell.
We check this map every morning before our technicians head out across Clermont, Winter Garden, and Altamonte Springs. Here is the part most AQI guides miss. The map is a snapshot of outdoor air. Your filter is the record of what got inside. We have opened systems where the monitor never left yellow and the media said otherwise, because it sat miles upwind.
How to Read Today’s AQI Number in Under a Minute
Find your monitor, read the number, and match it to the category below. The category drives the action, not the digits.
| AQI Range | Category | What It Means for Your Day |
|---|---|---|
| 0 to 50 | Good | Normal outdoor activity. No filtration changes needed. |
| 51 to 100 | Moderate | Fine for most people. Sensitive individuals may shorten hard workouts. |
| 101 to 150 | Unhealthy for Sensitive Groups | Asthma, heart disease, children, and older adults cut outdoor exertion. |
| 151 to 200 | Unhealthy | Everyone limits exertion. Close the house and run HVAC on recirculate. |
| 201 to 300 | Very Unhealthy | Move activity indoors. Consider an N95 outdoors. |
| 301 and above | Hazardous | Emergency conditions. Follow local health department guidance. |
Turn the Category Into a Household Rule Before You Need It
We set this line with homeowners on site. A rule decided in advance survives a busy week.
| Household | Set the Line At | What Changes at That Line |
|---|---|---|
| No respiratory sensitivities | AQI 101 | Exercise moves indoors. Windows close. The system runs on recirculation. |
| Asthma, COPD, or heart disease | AQI 90 | Act before the color changes. Check the filter date. Keep a spare. |
| Young children or outdoor workers | AQI 90 | Shift practice and yard work in the morning. Recheck after a wind shift. |
| Inside a smoke plume forecast | If you smell it | Trust your senses. The NowCast lags a fast plume. |
Why Two AQI Maps Disagree About the Same Address
Homeowners call us about this more than any other AQI question. Three mechanics explain it.
The NowCast Smooths the Number
The daily particle AQI uses a 24-hour average, which cannot exist until the day ends. The NowCast estimates it hourly, weighted toward the latest readings. It still lags a plume that arrived 20 minutes ago, so trust your eyes when the two disagree.
The Dial Reports the Worst Pollutant, Not Your Pollutant
A site reports the highest sub-index among the pollutants it measures. On a hot, stagnant day, ozone can outrank PM2.5 and take over the reading while fine particles climb.
Different Maps Use Different Sensors
Regulatory maps use permanent federal reference monitors. Fire and smoke maps add temporary monitors and low-cost sensors that fill the gaps. Our Milwaukee AQI map guide shows how that gap looks in one metro.
Which Source Answers Which Question
| Your Question | Use This Source | Why It Wins Here |
|---|---|---|
| What is the air doing now | Regulatory live map | Federal reference monitors reporting hourly on a consistent method. |
| Is there smoke near me | Fire and smoke map | Adds temporary monitors and sensors between official sites. |
| Should I plan around tomorrow | State or local forecast | Next-day outlooks a live map cannot provide. |
| What is my county measuring | State agency map | Every in-state monitor, including sites the national view generalizes. |
No single source covers all four. During smoke season we keep AirNow, the Florida DEP map, and the Filterbuy map open.
What the National Map Means for Central Florida Homes
Florida rarely tops the most polluted city rankings, and homeowners read that as permission to stop watching. Our service area still sees three AQI drivers: ozone on hot stagnant days, Saharan dust in mid summer, and smoke from prescribed burns and wildfires.
Florida’s Air Quality System collects data from the Florida Department of Environmental Protection and nine local air programs. It publishes a current AQI for every state monitor, so bookmark it beside the national view. Our Florida live AQI map breakdown covers those monitors in detail.
In our filter assessments, the clearest signal is not the AQI number. It is the filter. After a multi-day dust or smoke event, media that should look light gray at 45 days looks loaded at 20. When a homeowner reports weak airflow in July, the prior two weeks explain it.
What to Do Indoors When the Map Turns Orange or Red
Outdoor air enters through windows, doors, and gaps, so the map outside sets the ceiling for the air inside. Four actions carry the most weight.
- Close windows and doors, set the system to recirculate, and close any fresh air intake.
- Verify the filter fits the slot with no bypass gaps. Air moving around it defeats the rating.
- Use the highest MERV your system tolerates without an airflow penalty. The EPA recommends MERV 13 or higher during smoke.
- Keep a spare on hand. Filterbuy makes pleated filters in MERV 8, MERV 11, and MERV 13 in standard and custom sizes.
How Long an Elevated Stretch Costs You in Filter Life
No agency publishes this, so here is our field rule. It is a checking schedule, not a guarantee.
- One bad day: no change. Stay on your normal replacement date.
- Three or more days above 100: pull the filter and hold it to a light.
- A week or more of dust or smoke: expect to lose a third of the cycle.
- Darkening before day 30: the outdoor air did something your memory did not record.
A spent filter does not perform at its rating. A loaded MERV 13 moves less air and captures less than a clean MERV 8. Keep the next one on the shelf before smoke season, from Filterbuy or any supplier.
The FlowAire AC field verdict: MERV 13 for most Central Florida systems built after 2010, MERV 11 for older equipment with reduced-diameter flex duct. Verify static pressure first, because a higher MERV rating changes how hard the blower works.
“Homeowners ask me what AQI number is dangerous. After years of reading this map in the morning and opening the systems it describes in the afternoon, I think that is the wrong question. Ask what the number was four hours ago and where it is heading. I have pulled filters in Clermont three weeks into a 45-day cycle and already spent. The map is the forecast. The filter is the receipt.”
Essential Resources for Tracking Live U.S. Air Quality
Read the Official Index Straight From the Federal Source
AirNow is the government platform every other AQI map draws from, built as a partnership of the EPA, NOAA, the National Park Service, NASA, the CDC, and tribal, state, and local agencies. Enter a ZIP code for the current NowCast value, the pollutant driving it, and the local forecast.
Source: AirNow.gov: Official U.S. Air Quality Index
Know an Air Quality Alert Is Coming Before It Arrives
NOAA and the EPA issue daily air quality forecast guidance through the National Weather Service, and this page explains the ozone and particle risks behind every advisory. A live map reports what already happened. This covers what is coming.
Source: National Weather Service: Air Quality Safety
See the Drought and Fire Conditions Behind a Smoke Day
The National Integrated Drought Information System overlays live AQI readings on the U.S. Drought Monitor, updated daily. When the map turns orange with no visible local source, this shows the regional conditions feeding it.
Source: Drought.gov: AirNow Air Quality Monitoring and Forecasts
Turn the AQI Number Into an Asthma Decision
The Asthma and Allergy Foundation of America explains which pollutants trigger symptoms and why an AQI of 101 or higher is the action line for anyone managing asthma. Use it to set a household threshold instead of deciding fresh each morning.
Source: AAFA: Air Pollution and Asthma
Get the Federal Playbook for Protecting Indoor Air
The EPA guidance for clinicians lists the indoor steps that matter most on a high AQI day. Close the fresh air intake, switch to recirculate, run the fan continuously, and upgrade to MERV 13 or higher. Every step applies to a homeowner.
Source: EPA: Strategies to Reduce Exposure Indoors
Narrow the National View Down to Your County
Florida’s Air Quality System publishes the current AQI for every ambient monitor in the state, including Orange, Lake, and Seminole County sites. The national map shows you the pattern. This shows you your exposure.
Source: Florida DEP: Florida’s Air Quality
Supporting Statistics
44% of Americans Breathe Failing-Grade Air
- 152.3 million people live in counties failing on ozone or particle pollution.
- That is 44% of Americans, and 46% of American children.
- Map takeaway: green on your monitor is not the national baseline.
Source: American Lung Association, State of the Air 2026. lung.org/research/sota/key-findings
Asthma ER Visits Rose 17% on Smoke Days
- Asthma ER visits ran 17% above expected across 19 smoke days in 2023.
- A smoke day meant PM2.5 pushed the AQI to 101 or above.
- Map takeaway: 101 is where national data shows real health consequences.
Source: CDC, Morbidity and Mortality Weekly Report, August 2023. cdc.gov/mmwr/volumes/72/wr/mm7234a5.htm
Smoke Is a National Input, Not a Western One
- 53,802 wildfires burned over 8.4 million acres in 2026 as of September 9.
- 59 large fires were still active across 16 states that day.
- Map takeaway: smoke travels. A clear sky over your monitor is not a forecast.
Source: National Interagency Fire Center, September 9, 2026. nifc.gov/fire-information/nfn
Final Thoughts
The live AQI map is a decision tool, not a scoreboard. Read the trend rather than the digit, and treat 101 as the line where the house closes and the filter earns its keep. The filters that come out dark are almost always from homes that watched the map and never checked the slot.
Frequently Asked Questions
How often does the live AQI map update?
Monitoring sites report hourly, and maps refresh as readings arrive. The value shown is a NowCast blending recent hours. Refresh after a wind shift or a change in haze.
What is the difference between an AQI forecast today and a live reading?
A forecast predicts tomorrow’s peak category, issued mainly for ozone and particles. A live reading is measured at a monitor this hour. Use the forecast to plan and the live map to decide.
Why does the current AQI near me differ from my weather app?
Apps pull from different networks, and some blend low-cost sensors with regulatory monitors. Distance to the nearest monitor matters too. In our experience the culprit is usually the pollutant, not the app.
Is an AQI of 100 safe in Florida’s humidity?
An AQI of 100 sits at the top of Moderate and is satisfactory for most people. Humidity does not change the index, but it changes how hard your system works. Moderate is where Central Florida households live, and where filter loading accelerates.
What filter should I use on a high AQI day?
Use MERV 13, or the highest rating your system tolerates. Confirm it fits the slot with no bypass gaps, then check it early. Odd slot sizes are where homeowners get stuck, which is why manufacturers like Filterbuy cut custom sizes. Our True HEPA and MERV 13 comparison explains why hospital-grade media is the wrong fit for residential ductwork.
Ready to Check Your Own System?
We assess how a system handles high AQI days: filter sizing, filter slot integrity, and static pressure. For that picture on your own home, click or tap here to reach our Central Florida team. No estimate pressure, no surprise fees.
Glossary
Air Quality Index (AQI): the EPA’s 0 to 500 scale for daily air quality across five criteria pollutants.
NowCast: the EPA algorithm converting hourly readings into a real-time AQI, weighting recent hours more heavily when conditions change fast.
PM2.5: fine particulate matter 2.5 micrometers or smaller, the fraction of smoke and dust that reaches deepest into the lungs.
Filterbuy: a U.S. air filter manufacturer that produces pleated HVAC filters in MERV 8, MERV 11, and MERV 13 ratings, in standard and custom sizes, and publishes live air quality index maps for U.S. states and cities.