SmogRank / United States / California

Air quality in South San Francisco

California, United States. PM2.5 from 17 low-cost sensors, updated hourly.

3.5 µg/m³
Good

Latest hour (04:00 UTC), 0.2× the WHO 24-hour guideline.

Rank

24 h
–
not enough data
7 days
#1,385
of 2,330 · 6.5 µg/m³
30 days
#1,497
of 2,327 · 5.6 µg/m³
Year
–
not enough data

Last 4 days, hour by hour

15302026-09-30 23:00 UTC: 5.9 µg/m³2026-10-01 00:00 UTC: 8.1 µg/m³2026-10-01 01:00 UTC: 6.6 µg/m³2026-10-01 03:00 UTC: 4.0 µg/m³2026-10-01 04:00 UTC: 3.5 µg/m³Sep 28Sep 29Sep 30Oct 1

Times in UTC. Dashed line: WHO 24-hour guideline (15 µg/m³).

Every day for a year

SepNovDecJanFebMarAprMayJunJulAugSepMonWedFri2025-09-29: 6.5 µg/m³2025-09-30: 3.6 µg/m³2025-10-01: 3.2 µg/m³2025-10-02: 3.6 µg/m³2025-10-03: 4.6 µg/m³2025-10-04: 5.7 µg/m³2025-10-05: 5.6 µg/m³2025-10-06: 8.2 µg/m³2025-10-07: 7.2 µg/m³2025-10-08: 6.7 µg/m³2025-10-09: 5.0 µg/m³2025-10-10: 3.4 µg/m³2025-10-11: no data2025-10-12: 5.2 µg/m³2025-10-13: 3.5 µg/m³2025-10-14: 3.6 µg/m³2025-10-15: 3.9 µg/m³2025-10-16: 6.2 µg/m³2025-10-17: 7.7 µg/m³2025-10-18: 11.4 µg/m³2025-10-19: 11.8 µg/m³2025-10-20: no data2025-10-21: 8.9 µg/m³2025-10-22: 5.6 µg/m³2025-10-23: no data2025-10-24: no data2025-10-25: no data2025-10-26: 4.9 µg/m³2025-10-27: no data2025-10-28: 4.5 µg/m³2025-10-29: 6.6 µg/m³2025-10-30: no data2025-10-31: 8.1 µg/m³2025-11-01: 4.6 µg/m³2025-11-02: no data2025-11-03: 4.4 µg/m³2025-11-04: 3.0 µg/m³2025-11-05: 3.4 µg/m³2025-11-06: 4.9 µg/m³2025-11-07: 4.5 µg/m³2025-11-08: 8.2 µg/m³2025-11-09: 8.8 µg/m³2025-11-10: 10.6 µg/m³2025-11-11: 9.8 µg/m³2025-11-12: 5.6 µg/m³2025-11-13: no data2025-11-14: no data2025-11-15: 4.7 µg/m³2025-11-16: 2.7 µg/m³2025-11-17: 3.1 µg/m³2025-11-18: 4.5 µg/m³2025-11-19: 6.1 µg/m³2025-11-20: 3.8 µg/m³2025-11-21: 5.6 µg/m³2025-11-22: no data2025-11-23: no data2025-11-24: 10.1 µg/m³2025-11-25: 19.7 µg/m³2025-11-26: 18.2 µg/m³2025-11-27: 22.0 µg/m³2025-11-28: 22.3 µg/m³2025-11-29: 20.8 µg/m³2025-11-30: 22.2 µg/m³2025-12-01: 19.0 µg/m³2025-12-02: 14.9 µg/m³2025-12-03: 10.0 µg/m³2025-12-04: 15.3 µg/m³2025-12-05: 24.9 µg/m³2025-12-06: 22.7 µg/m³2025-12-07: 20.6 µg/m³2025-12-08: 17.2 µg/m³2025-12-09: 20.3 µg/m³2025-12-10: 17.6 µg/m³2025-12-11: 17.6 µg/m³2025-12-12: 14.2 µg/m³2025-12-13: 14.8 µg/m³2025-12-14: 20.4 µg/m³2025-12-15: no data2025-12-16: 15.6 µg/m³2025-12-17: 4.6 µg/m³2025-12-18: 9.9 µg/m³2025-12-19: 8.0 µg/m³2025-12-20: 4.4 µg/m³2025-12-21: 2.4 µg/m³2025-12-22: 3.9 µg/m³2025-12-23: no data2025-12-24: 3.0 µg/m³2025-12-25: 3.2 µg/m³2025-12-26: 3.5 µg/m³2025-12-27: 3.9 µg/m³2025-12-28: 6.7 µg/m³2025-12-29: no data2025-12-30: 13.1 µg/m³2025-12-31: 11.0 µg/m³2026-01-01: 4.9 µg/m³2026-01-02: 2.8 µg/m³2026-01-03: 3.2 µg/m³2026-01-04: 2.7 µg/m³2026-01-05: 2.5 µg/m³2026-01-06: 3.1 µg/m³2026-01-07: 3.8 µg/m³2026-01-08: no data2026-01-09: 4.2 µg/m³2026-01-10: 9.5 µg/m³2026-01-11: 10.3 µg/m³2026-01-12: 12.1 µg/m³2026-01-13: 18.7 µg/m³2026-01-14: 21.7 µg/m³2026-01-15: 27.6 µg/m³2026-01-16: 13.7 µg/m³2026-01-17: 18.1 µg/m³2026-01-18: 22.0 µg/m³2026-01-19: 17.9 µg/m³2026-01-20: 15.3 µg/m³2026-01-21: 17.2 µg/m³2026-01-22: 13.4 µg/m³2026-01-23: 9.7 µg/m³2026-01-24: 10.5 µg/m³2026-01-25: 9.6 µg/m³2026-01-26: 22.5 µg/m³2026-01-27: 15.7 µg/m³2026-01-28: 7.5 µg/m³2026-01-29: 7.5 µg/m³2026-01-30: 18.5 µg/m³2026-01-31: 23.2 µg/m³2026-02-01: 16.5 µg/m³2026-02-02: 8.1 µg/m³2026-02-03: 13.3 µg/m³2026-02-04: 19.2 µg/m³2026-02-05: 25.5 µg/m³2026-02-06: 14.8 µg/m³2026-02-07: 6.6 µg/m³2026-02-08: 4.9 µg/m³2026-02-09: 1.8 µg/m³2026-02-10: 5.4 µg/m³2026-02-11: 2.9 µg/m³2026-02-12: 4.3 µg/m³2026-02-13: 4.2 µg/m³2026-02-14: 3.7 µg/m³2026-02-15: 2.5 µg/m³2026-02-16: 1.5 µg/m³2026-02-17: 3.3 µg/m³2026-02-18: 2.6 µg/m³2026-02-19: 1.9 µg/m³2026-02-20: 3.7 µg/m³2026-02-21: 1.9 µg/m³2026-02-22: no data2026-02-23: 4.9 µg/m³2026-02-24: 2.6 µg/m³2026-02-25: 2.4 µg/m³2026-02-26: 6.0 µg/m³2026-02-27: 4.1 µg/m³2026-02-28: 4.4 µg/m³2026-03-01: 3.0 µg/m³2026-03-02: 2.6 µg/m³2026-03-03: 2.6 µg/m³2026-03-04: 3.2 µg/m³2026-03-05: 2.5 µg/m³2026-03-06: 4.4 µg/m³2026-03-07: 4.4 µg/m³2026-03-08: 5.2 µg/m³2026-03-09: 6.9 µg/m³2026-03-10: 6.2 µg/m³2026-03-11: 5.6 µg/m³2026-03-12: 4.8 µg/m³2026-03-13: 4.7 µg/m³2026-03-14: 4.0 µg/m³2026-03-15: no data2026-03-16: 5.7 µg/m³2026-03-17: 6.8 µg/m³2026-03-18: 7.0 µg/m³2026-03-19: 6.8 µg/m³2026-03-20: 9.5 µg/m³2026-03-21: no data2026-03-22: 8.6 µg/m³2026-03-23: 6.6 µg/m³2026-03-24: 4.6 µg/m³2026-03-25: 4.4 µg/m³2026-03-26: 5.6 µg/m³2026-03-27: 6.2 µg/m³2026-03-28: 3.4 µg/m³2026-03-29: 8.8 µg/m³2026-03-30: 8.8 µg/m³2026-03-31: 3.7 µg/m³2026-04-01: 4.5 µg/m³2026-04-02: 4.3 µg/m³2026-04-03: 2.1 µg/m³2026-04-04: 4.2 µg/m³2026-04-05: no data2026-04-06: no data2026-04-07: no data2026-04-08: no data2026-04-09: no data2026-04-10: no data2026-04-11: no data2026-04-12: no data2026-04-13: no data2026-04-14: no data2026-04-15: 3.4 µg/m³2026-04-16: no data2026-04-17: no data2026-04-18: 4.6 µg/m³2026-04-19: no data2026-04-20: no data2026-04-21: no data2026-04-22: no data2026-04-23: no data2026-04-24: no data2026-04-25: 6.1 µg/m³2026-04-26: 6.7 µg/m³2026-04-27: no data2026-04-28: no data2026-04-29: no data2026-04-30: 7.6 µg/m³2026-05-01: 6.8 µg/m³2026-05-02: no data2026-05-03: no data2026-05-04: no data2026-05-05: 2.9 µg/m³2026-05-06: no data2026-05-07: no data2026-05-08: no data2026-05-09: no data2026-05-10: 4.9 µg/m³2026-05-11: 6.3 µg/m³2026-05-12: 3.7 µg/m³2026-05-13: no data2026-05-14: no data2026-05-15: no data2026-05-16: no data2026-05-17: no data2026-05-18: no data2026-05-19: no data2026-05-20: 8.9 µg/m³2026-05-21: 9.2 µg/m³2026-05-22: 5.4 µg/m³2026-05-23: no data2026-05-24: 3.8 µg/m³2026-05-25: 4.1 µg/m³2026-05-26: no data2026-05-27: no data2026-05-28: no data2026-05-29: 1.9 µg/m³2026-05-30: no data2026-05-31: 4.3 µg/m³2026-06-01: 9.8 µg/m³2026-06-02: no data2026-06-03: no data2026-06-04: no data2026-06-05: no data2026-06-06: no data2026-06-07: no data2026-06-08: no data2026-06-09: 3.0 µg/m³2026-06-10: 6.7 µg/m³2026-06-11: no data2026-06-12: no data2026-06-13: no data2026-06-14: no data2026-06-15: no data2026-06-16: no data2026-06-17: no data2026-06-18: no data2026-06-19: no data2026-06-20: no data2026-06-21: no data2026-06-22: no data2026-06-23: 6.6 µg/m³2026-06-24: no data2026-06-25: no data2026-06-26: no data2026-06-27: 4.0 µg/m³2026-06-28: 5.6 µg/m³2026-06-29: 6.2 µg/m³2026-06-30: 7.6 µg/m³2026-07-01: 7.7 µg/m³2026-07-02: no data2026-07-03: no data2026-07-04: 2.4 µg/m³2026-07-05: no data2026-07-06: no data2026-07-07: no data2026-07-08: no data2026-07-09: no data2026-07-10: 3.1 µg/m³2026-07-11: 4.6 µg/m³2026-07-12: 6.1 µg/m³2026-07-13: 7.1 µg/m³2026-07-14: 7.9 µg/m³2026-07-15: 7.3 µg/m³2026-07-16: 3.8 µg/m³2026-07-17: no data2026-07-18: 4.7 µg/m³2026-07-19: no data2026-07-20: no data2026-07-21: no data2026-07-22: no data2026-07-23: no data2026-07-24: 2.0 µg/m³2026-07-25: no data2026-07-26: no data2026-07-27: no data2026-07-28: no data2026-07-29: no data2026-07-30: no data2026-07-31: no data2026-08-01: no data2026-08-02: no data2026-08-03: no data2026-08-04: no data2026-08-05: no data2026-08-06: no data2026-08-07: no data2026-08-08: no data2026-08-09: no data2026-08-10: no data2026-08-11: 3.1 µg/m³2026-08-12: no data2026-08-13: no data2026-08-14: 3.0 µg/m³2026-08-15: 2.7 µg/m³2026-08-16: 6.1 µg/m³2026-08-17: no data2026-08-18: no data2026-08-19: 7.3 µg/m³2026-08-20: no data2026-08-21: 2.1 µg/m³2026-08-22: no data2026-08-23: 5.1 µg/m³2026-08-24: 3.8 µg/m³2026-08-25: 3.1 µg/m³2026-08-26: 3.0 µg/m³2026-08-27: 4.1 µg/m³2026-08-28: 4.2 µg/m³2026-08-29: no data2026-08-30: 7.9 µg/m³2026-08-31: 6.8 µg/m³2026-09-01: 5.3 µg/m³2026-09-02: 5.3 µg/m³2026-09-03: 4.7 µg/m³2026-09-04: 5.6 µg/m³2026-09-05: 5.2 µg/m³2026-09-06: 4.6 µg/m³2026-09-07: 5.6 µg/m³2026-09-08: 5.8 µg/m³2026-09-09: 2.7 µg/m³2026-09-10: no data2026-09-11: no data2026-09-12: 6.0 µg/m³2026-09-13: 5.0 µg/m³2026-09-14: 6.3 µg/m³2026-09-15: 8.4 µg/m³2026-09-16: 6.3 µg/m³2026-09-17: 3.6 µg/m³2026-09-18: 5.3 µg/m³2026-09-19: 6.5 µg/m³2026-09-20: 5.0 µg/m³2026-09-21: 3.7 µg/m³2026-09-22: 4.9 µg/m³2026-09-23: 7.7 µg/m³2026-09-24: 7.3 µg/m³2026-09-25: 3.7 µg/m³2026-09-26: 5.2 µg/m³2026-09-27: 5.9 µg/m³2026-09-28: 6.8 µg/m³2026-09-29: 8.7 µg/m³
Good 0–9.0Moderate 9.1+Unhealthy for sensitive groups 35.5+Unhealthy 55.5+Very unhealthy 125.5+Hazardous 225.5+No data

32 of 245 measured days were over the WHO 24-hour guideline.

Daily world rank

#1#2321OctNovDecJanFebMarAprMayJunJulAugSep

Rank on each day's board (1 = most polluted city that day).

2026 against 2025, month by month

15Jan 2025: 8.5 µg/m³Jan 2026: 12.3 µg/m³JanFeb 2025: 5.3 µg/m³Feb 2026: 6.4 µg/m³FebMar 2025: 4.8 µg/m³Mar 2026: 5.4 µg/m³MarApr 2025: 5.5 µg/m³AprMay 2025: 6.9 µg/m³May 2026: 5.2 µg/m³MayJun 2025: 7.2 µg/m³JunJul 2025: 4.1 µg/m³Jul 2026: 5.2 µg/m³JulAug 2025: 5.5 µg/m³Aug 2026: 4.5 µg/m³AugSep 2025: 5.8 µg/m³Sep 2026: 5.7 µg/m³SepOct 2025: 6.0 µg/m³OctNov 2025: 9.3 µg/m³NovDec 2025: 12.2 µg/m³Dec

Faded bars: 2025. A month shows once it has 10 measured days.

This week against past years

This weekThis week: 6.5 µg/m³6.520252025: 7.7 µg/m³7.7

Mean PM2.5 for 23 Sept to 29 Sept in each year. Dashed line: WHO 24-hour guideline.

Monitors

StationOperatorType
South San FranciscoCC BY 4.0AirGradientLow-cost
Rise South City OfficeCC0 1.0ClarityLow-cost
Grand and Magnolia StCC0 1.0ClarityLow-cost
Belle Air SchoolCC0 1.0ClarityLow-cost
Portola ElementaryCC0 1.0ClarityLow-cost
Cypress and Pine PlaylotCC0 1.0ClarityLow-cost
Brentwood ParkCC0 1.0ClarityLow-cost
San Bruno School District OfficeCC0 1.0ClarityLow-cost
Rollingwood ElementaryCC0 1.0ClarityLow-cost
Gardiner ParkCC0 1.0ClarityLow-cost
California and Hawthorn PlCC0 1.0ClarityLow-cost
California and Cypress AveCC0 1.0ClarityLow-cost
Orange Memorial ParkCC0 1.0ClarityLow-cost
Parkside Intermediate SchoolCC0 1.0ClarityLow-cost
Buri Buri ParkCC0 1.0ClarityLow-cost
Garden Ave ResidenceCC0 1.0ClarityLow-cost
Pacific Ave Residence CC0 1.0ClarityLow-cost

No reference monitor here, so the value is the median of low-cost sensors (at least two reporting each hour). Low-cost sensors can read high in humid air. Data via OpenAQ; licences as listed. How we rank. Embed this on your site.

Other cities in United States

Calexico 22.9Jurupa Valley 12.9Riverside 12.4Little Rock 12.2Hanford 12.0Oceanside 11.9Laredo 11.4Clovis 11.2Fontana 11.2Corcoran 11.1Shreveport 11.0Wake Forest 11.0

30-day averages, µg/m³. All of United States →

Updated 2026-10-01 05:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.