Foster City, CA Air Quality Today
Friday, July 17, 2026 · Data: WeatherAPI • EPA
Air quality in Foster City is Good today, July 17. Fine particle and ozone readings are both low right now. Open the windows and keep your plans outside.
Level 1 of 6 on the EPA scale
What's in Foster City's Air Right Now
PM2.5 (fine particles): 10 µg/m³. Anything under 12 µg/m³ counts as clean, so fine particles aren't a concern right now. These particles come from exhaust and smoke and are small enough to reach deep into your lungs.
PM10 (coarse dust): 15 µg/m³. Readings under 54 µg/m³ rate Good. Dust and pollen fragments ride in this size range and irritate your nose and throat.
Ozone: 52 µg/m³. Ozone forms when sunlight cooks car exhaust, so hot afternoons read worst, usually between 2 PM and 7 PM. Mornings stay cleanest.
Nitrogen dioxide: 10.2 µg/m³. NO2 comes almost entirely from traffic and feeds afternoon ozone. Readings run highest near busy roads during the morning and evening commutes.
Is It Safe to Go Outside in Foster City Today?
Yes. The air in Foster City is clean today. Open the windows and keep your run outside. Kids can stay out as long as they want.
Days like this are worth using. If a long walk or a hard workout is on your list this week, today is the day for it.
Air Quality and Pollen Are Two Different Numbers
The air quality index tracks pollution: ozone, dust, smoke, and exhaust. Pollen isn't part of the score, so a Good air day in Foster City can still be a rough allergy day.
Right now the biggest pollen load in Foster City is grass pollen, rated High. If your eyes itch while the air reads clean, pollen is the likely culprit.
Check today's Foster City, CA pollen count →Frequently Asked Questions
What is the AQI in Foster City right now?
Today's air in Foster City is rated Good, level 1 of 6 on the EPA scale. That's the cleanest category, with no limits on outdoor plans. The reading updates daily, so check back before you head out.
Is it safe to exercise outside in Foster City today?
Yes. Clean air puts no limit on outdoor exercise today. Morning is still the best window in summer, since ozone builds through hot afternoons.
Does Foster City have an air quality alert today?
Official alerts come from AirNow.gov and your state air agency, and MyPollenPal doesn't track them directly. Today's EPA category in Foster City is Good. Days rated Unhealthy for Sensitive Groups or worse usually line up with an official alert.
Sources
- U.S. Environmental Protection Agency / AirNow. "AQI Basics." airnow.gov
- U.S. Environmental Protection Agency. "Particulate Matter (PM) Basics." epa.gov
- U.S. Environmental Protection Agency. "Ground-level Ozone Basics." epa.gov
Air Quality Is Half the Picture
Pollen fills in the rest. See today's tree, grass, and weed levels for Foster City, or sign up for a morning email on days when pollen runs High or Very High.