San Mateo, CA
Long-term air quality
What this page tells you
This page combines annual PM2.5, unhealthy days, 5-year trend, and data coverage so you can compare long-term air quality, not just today's reading.
San Mateo, CA air quality summary: San Mateo, CA receives a clean air score of 79.7 and a grade of B, indicating healthy long-term air quality. The city's annual mean for PM2.5 is 6.6 µg/m³. In San Mateo, the annual mean concentration of PM2.5 is 6.6 µg/m³. Long-term air quality in San Mateo has been improving over recent years.
Clean Air Score
A clean air score of 79.7 and a grade of B signify that San Mateo has relatively low long-term particulate exposure. These ratings reflect a generally healthy environment for residents over time.
🏡 What This Means for Buying
Air quality is a reliable positive factor for residents in San Mateo. The B grade reflects a level of pollution that is considered moderate and generally acceptable for long-term living.
Indoor Air Quality in San Mateo, CA
Outdoor pollution can still affect indoor air when windows are open, filtration is weak, or wildfire smoke moves in.
How to react when today's AQI changes
Use the AQI bands below to decide whether to open windows, run an air purifier, or stay indoors when pollution spikes in San Mateo.
AQI 0-50
GoodOpen windows: Open windows if you want fresh air.
Air purifier: No purifier needed for most homes.
Indoor activity: Normal indoor activity is fine.
AQI 51-100
ModerateOpen windows: Sensitive groups should limit open-window time.
Air purifier: Use fans or filtration if dust or pollen is bothering you.
Indoor activity: Most people can stay active indoors.
AQI 101-150
Unhealthy for Sensitive GroupsOpen windows: Keep windows closed.
Air purifier: Run a HEPA purifier in the main room and bedroom.
Indoor activity: Sensitive groups should reduce outdoor exposure.
AQI 151+
UnhealthyOpen windows: Keep windows and doors closed.
Air purifier: Run HEPA continuously and seal obvious drafts.
Indoor activity: Stay indoors as much as possible; use an N95 if you must go out.
Common indoor air concerns in San Mateo:
- Wildfire smoke infiltration (PM2.5)
- Seasonal pollen and dust mite allergens
- VOCs from household products
Recommended action: If today's AQI reaches 101 or higher, close windows and run HEPA filtration before indoor air starts to feel smoky or stale.
Top Products for San Mateo Homes:
🩺 My Health Risk Assessment
See how San Mateo's air quality affects you and your family specifically.
Health Advice
Enjoy the outdoors! Air quality is great.
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</> Create Free Widget🏡 Property Value Impact Analysis
Between 2019 and 2024, San Mateo's air quality improved by 1 μg/m³. Based on NBER studies, this change correlates with a estimated 4% increase in relative property value retention.
Cleaner Alternatives in CA
Why San Mateo earned a 79.7
Raw inputs, scoring weights, and data coverage for this city.
Best Time to Run
Find the cleanest hours for your run today.
Cycling Forecast
Avoid pollution spikes on your next ride.
📅 Past 30 Days Trend
Real-time daily PM2.5 AQI
🌸 Pollen Outlook
Current Seasonal Forecast
How it worksBased on current seasonal forecast data. Not a long-term pollution rating or relocation score.
Score Breakdown
| Component | Weight | Score Contribution |
|---|---|---|
| Annual Air Quality | 40% | 76.6 |
| Unhealthy Days | 25% | 100 |
| 5-Year Trend | 20% | 55 |
| Seasonal Variability | 10% | 90.8 |
| Extreme Events | 5% | 100 |
Explore More Air Quality Data
Frequently Asked Questions
About This Data
Data Sources
Historical air quality mapping and scoring are based completely on official U.S. Environmental Protection Agency (EPA) AirNow API data. 5-day AQI forecasts are provided by WAQI.
Methodology
Our Clean Air Score (0-100) is a proprietary algorithm that weighs multiple factors:
- Annual PM2.5 averages (40%)
- Frequency of unhealthy days (25%)
- 5-year pollution trends (20%)
- Seasonal variability and extreme events (15%)
Updates & Accuracy
Real-time data is updated hourly. Historical aggregate scores are recalculated monthly to reflect the latest trends. While we strive for accuracy, sensor maintenance and local conditions can affect individual readings.
Practical Advice
When AQI > 100: Sensitive groups (children, elderly, asthmatics) should limit prolonged outdoor exertion.
When AQI > 150: Everyone should avoid outdoor exercise and keep windows closed.
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San Mateo Air Quality FAQs
Is San Mateo a good fit for people who care about long-term air quality?
San Mateo is a solid choice, carrying a clean air score of 79.7 and a grade of B. Its PM2.5 annual mean of 6.6 µg/m³ represents relatively low long-term particulate exposure.
How frequent is unhealthy air in San Mateo?
San Mateo reports 0% of days as unhealthy, which supports its B grade and PM2.5 annual mean of 6.6 µg/m³. Residents enjoy consistently high air quality standards.
Is air quality in San Mateo improving or getting worse over time?
The long-term air quality trend in San Mateo has been improving in recent years, indicating a positive direction for long-term conditions.
Does air quality vary within San Mateo?
Air quality within San Mateo can vary based on local traffic, industry, and location patterns.