SmogRank / Mecca / San Francisco
Mecca vs San Francisco: PM2.5 compared
Over the last year, Mecca's air was about 1.9× as polluted as San Francisco's: PM2.5 averaged 12.6 µg/m³ against 6.8, on the 69 days both cities were measured. Mecca had the dirtier air on 50 of those days, San Francisco on 19. Mecca was over the WHO's daily guideline of 15 µg/m³ on 22 of them, San Francisco on 0.
Right now
The last year, day by day
Month by month
Each city's worst days
Mecca
- 21 May 202614854.6 µg/m³
- 16 May 202613047.2 µg/m³
- 18 May 20269733.8 µg/m³
San Francisco
- 20 May 20266114.5 µg/m³
- 15 May 20266014.1 µg/m³
- 19 May 20265913.5 µg/m³
Daily means in US AQI, with µg/m³ beside them, since the index stops at its top value, over the days both cities were measured in the last year. Each date opens that day's world board.
Compare either city with another
Mecca
Side by side with Indio (the nearest), Hanford (United States's 2nd worst on 30 days), Gujranwala (the world's worst on 30 days).
San Francisco
Side by side with South San Francisco (the nearest), Gujranwala (the world's worst on 30 days).
Use this page
SmogRank, PM2.5 daily means compared, Mecca and San Francisco, 7 Oct 2025 – 6 Oct 2026, smogrank.com/compare/us-mecca/us-san-francisco (accessed 7 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
The same rules as every SmogRank figure: reference monitors first, and a day counts with 18 measured hours. How we measure.
Updated 2026-10-07 08:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.