Boulder vs Mecca: PM2.5 compared
Over the last year, Mecca's air was about 3.4× as polluted as Boulder's: PM2.5 averaged 12.1 µg/m³ against 3.6, on the 74 days both cities were measured. Mecca had the dirtier air on 64 of those days, Boulder on 10. Mecca was over the WHO's daily guideline of 15 µg/m³ on 22 of them, Boulder on 0.
Right now
The last year, day by day
Month by month
Each city's worst days
Boulder
- 15 Sept 2026468.3 µg/m³
- 1 Apr 2026427.5 µg/m³
- 2 Apr 2026366.4 µg/m³
Mecca
- 21 May 202614854.6 µg/m³
- 16 May 202613047.2 µg/m³
- 18 May 20269733.8 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
Boulder
Side by side with Longmont (the nearest), Gujranwala (the world's worst on 30 days).
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).
Use this page
SmogRank, PM2.5 daily means compared, Boulder and Mecca, 7 Oct 2025 – 6 Oct 2026, smogrank.com/compare/us-boulder/us-mecca (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.