Cambridge 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 Cambridge Air Today?
What High AQI Means for Your Lungs in Cambridge
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 Cambridge, MA Now
TL;DR:
The live map above shows the current Air Quality Index (AQI) for Cambridge, Massachusetts. Most days the air here is clean, but summer ozone and Canadian wildfire smoke can push it into unhealthy territory. Filterbuy has made air filters in the U.S. since 2013, and our advice comes from what we see in customers' filters: check which pollutant is leading, and have a MERV 13 filter and a portable HEPA air cleaner ready before smoke arrives.
Key Takeaways
The AQI runs from 0 to 500; orange or worse (101+) is unhealthy for at least some people.
Ozone is the main warm-season pollutant, while wildfire smoke, which carries fine particles called PM2.5, causes the sharpest spikes.
Cambridge's Middlesex County earned an A for daily particle pollution and a B for ozone in the American Lung Association's 2026 report.
Two-thirds of Cambridge homes are rentals, so your smoke-day setup depends on your building.
AQI 100 is Filterbuy's action line: MERV 13 in the HVAC, the fan set to "On," a portable HEPA air cleaner in each occupied room and the house closed up.
How to Read the Cambridge AQI Map Above
The map turns pollution readings into one color-coded number. Tap the ZIP code closest to you: 02138 (Harvard Square, West Cambridge), 02139 (Central Square, Cambridgeport, MIT), 02140 (Porter Square, North Cambridge), 02141 (East Cambridge) or 02142 (Kendall Square).
At Filterbuy, we check the dominant pollutant next, since ozone and PM2.5 need different responses. Ozone builds on hot afternoons and fades overnight, while PM2.5 can arrive with smoke at any hour and linger for days.
What Each Cambridge AQI Color Means and What to Do
The U.S. Environmental Protection Agency (EPA) uses six AQI categories, with PM2.5 ranges from its May 2024 update.
Source: U.S. EPA, AirNow AQI Basics (airnow.gov). PM2.5 ranges reflect EPA's 2024 breakpoint update.
Filterbuy's action line is AQI 100. EPA's orange category starts at 101. We act one point earlier. First check AirNow and MassAir Online for official guidance, then:
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.
Close the house up, and skip candles, frying, smoking and vacuuming while smoke is in.
No central HVAC? Portable HEPA air cleaners are your primary defense. At 201 and above, official guidance comes first, and filtration is one layer alongside it.
Why the Cambridge Reading Can Lag or Look Off
The Massachusetts Department of Environmental Protection (MassDEP) doesn't run a regulatory monitor inside Cambridge. The closest sits across the Charles at Kenmore Square, in use since 1965, and the nearest ozone monitor is in Roxbury. Two other things can skew it:
NowCast smoothing. AirNow weights recent hours, so a fast-moving plume can look worse outside than the number suggests.
The other Cambridges. Searches often mix up Cambridge, MA with Cambridge, England and Ontario, which issues its smoke closures separately.
Is the Air in Cambridge Safe to Breathe Today?
It depends on the color on the live map. At orange, the Cambridge Public Health Department suggests swapping a run for a walk and staying away from busy roads. At red or higher, everyone should cut back on exertion. If you have asthma, COPD or a heart condition, follow the plan from your doctor and official guidance.
Cambridge Air Quality Forecasts and What an Alert Day Means
MassDEP publishes the official forecast and alerts on MassAir Online. An Air Quality Alert means ozone or fine particles may reach the Unhealthy for Sensitive Groups level. Alerts often go out a day ahead, so move runs to the morning on ozone days and check your filter and spares before smoke arrives.
For a statewide view, see Filterbuy's Massachusetts air quality map.
Does Air Quality Differ Across Cambridge Neighborhoods?
Nitrogen dioxide builds up near busy roads, so blocks along Route 2, the Alewife Brook Parkway, Memorial Drive and the Turnpike's Charles River edge get more exhaust, and filtration is worth running there even on green days.
What Actually Pollutes Cambridge's Air
Two pollutants drive most readings, with traffic NO₂ adding a local layer:
Ground-level ozone. Ozone forms when exhaust from vehicles and smokestacks reacts in sunlight.
Fine particles (PM2.5). Cambridge Public Health lists cars, trucks, industrial emissions and wildfire smoke as the city's main sources. Since Middlesex County's daily particle levels rank among the cleanest in the country, a PM2.5 spike in Cambridge usually points to smoke.
How Cambridge's Air Compares with Greater Boston
In the American Lung Association's 2026 report, the Boston-Worcester-Providence area failed for both daily particle pollution and ozone, largely due to Essex County, MA and Washington County, RI (ALA).
Source: American Lung Association, "State of the Air" 2026 report (2022–2024 data).
Compare conditions on Filterbuy's Boston air quality map.
Canadian Wildfire Smoke: Cambridge's Biggest Wildcard
Smoke now drives most of Cambridge's unhealthy days. MassDEP's director of air and climate programs reported 7 to 12 alert days a year from 2020 to 2022, then 30 in 2023, largely from Canadian smoke. Recent episodes:
May 30, 2023: MassDEP alerted Middlesex and eight other counties as Nova Scotia smoke arrived.
July 1–2, 2023: Cambridge reported smoke-driven AQI in the Unhealthy for Sensitive Groups range.
July 15–16 and July 18, 2026: MassDEP issued statewide PM2.5 alerts as Canadian smoke returned.
We saw the 2023 smoke from the factory side, too: Massachusetts customers' filters came back nearly black after about two weeks. Follow incoming plumes on our Boston wildfire smoke map.
Your Cambridge Smoke-Day Plan, by Building Type
About 66.5% of Cambridge's occupied units are rented (Cambridge CDD), and about 47% were built in 1939 or earlier (U.S. Census ACS). Filterbuy makes HVAC filters, not portable air cleaners, so the purifier advice here isn't a sales pitch.
Shares reflect dwelling units in the city's June 2025 inventory. EPA's sizing chart calls for a CADR of about 195 for a 300-square-foot bedroom, roughly two-thirds of the floor area. EPA also advises against air cleaners that produce ozone, so skip ionizers and ozone generators. A DIY box fan with a MERV 13 filter is a reasonable stopgap; use a certified 2012-or-newer fan and don't leave it running unattended.
During smoke, check every filter often and replace it when it looks dirty, which can be well before the normal interval, and keep spares on hand. Cambridge Public Health warns that sealing up without air conditioning in extreme heat is dangerous; use a cooling center instead.
Supporting Statistics for Cambridge Households
Americans spend about 90% of their time indoors, where some pollutants run 2–5 times higher than outdoors (U.S. EPA).
11.9% of Massachusetts adults had asthma in 2023, above the 10.2% U.S. median (Massachusetts DPH).
A box fan with a MERV 13 filter cleaned smoke at a CADR of 111 cfm in EPA tests, but dirty filters barely worked (U.S. EPA).
Filterbuy's Take: Start with the Pollutant, Not the Product
On the few bad days, what matters is which pollutant you're up against. Michelle Wan, Filterbuy's Brand Manager and Air Quality Writer, explains it this way:
"The question I get most often is which one to buy. The question that actually decides it is what is coming at your house, and almost nobody asks that one first."
The households that handle smoke season best put in a fresh MERV 13 before summer and keep a spare on the shelf.
Which Filter the Cambridge AQI Calls For
MERV 8 or MERV 11 covers everyday dust and pollen. For smoke, the answer is MERV 13 in the HVAC plus a portable HEPA air cleaner in each occupied room, two layers doing different jobs. Ozone needs no filter change, since pleated filters capture particles and ozone is a gas.
EPA recommends a filter rated at least MERV 13 during smoke events, and says most furnaces and HVAC systems can accommodate MERV 13 without equipment problems, provided the filter is replaced frequently. HEPA belongs in portable air cleaners, never in a furnace slot.
Filterbuy makes MERV 13 air filters in 600+ sizes and 1-, 2- and 4-inch depths. Fit is the check that matters: Filterbuy reviewer David Clark, a licensed HVAC technician, asks homeowners for a photo of the empty slot rather than the old filter, since the old one often never fit, especially in older housing. You can measure your filter size or order Filterbuy custom air filters, cut to the eighth of an inch. For lingering odors, see Filterbuy's Odor Eliminator filters.
Cambridge Air Quality FAQs
What MERV rating do I need for wildfire smoke in Cambridge?
MERV 13. EPA recommends a filter rated MERV 13 or higher during smoke events. Filterbuy also recommends a portable HEPA air cleaner in each occupied room.
What is the air quality in Cambridge, MA today?
Today's Cambridge AQI, color category and leading pollutant appear in the live map at the top of this page.
Is the air quality bad in Cambridge today?
Cambridge air is unhealthy for sensitive groups at an AQI of 101 (orange) and for everyone at 151 (red). Filterbuy's action line is 100.
What is the Cambridge PM2.5 level today?
The live module shows PM2.5 when it leads, and MassAir Online posts hourly PM2.5 from the Kenmore Square monitor. A 24-hour average above 35.4 µg/m³ is unhealthy for sensitive groups.
When is Cambridge air quality usually worst?
Ozone peaks on hot summer afternoons, and recent smoke episodes have hit between late May and mid-July.
Glossary
AQI (Air Quality Index): EPA's 0–500 scale with six health categories.
PM2.5: Fine particles 2.5 micrometers or smaller that can reach deep into the lungs.
Ground-level ozone: Smog's main ingredient, formed when emissions react in sunlight.
NO₂ (nitrogen dioxide): A traffic-related gas that helps form ozone.
NowCast: EPA's recent-hours weighting for near-real-time AQI.
MassDEP: The Massachusetts Department of Environmental Protection, which monitors air and issues alerts.
MERV: Minimum Efficiency Reporting Value, a 1–16 rating of HVAC filter efficiency.
HEPA: High-efficiency particulate air filter, used in portable air cleaners.
CADR: Clean Air Delivery Rate, a purifier's filtered-air output.
Clean room: A closed room with a portable air cleaner that keeps smoke levels low.