SmogRank / Helena Valley West Central / Mecca
Helena Valley West Central vs Mecca: PM2.5 compared
Over the last year, Mecca's air was about 3.4× as polluted as Helena Valley West Central's: PM2.5 averaged 12.1 µg/m³ against 3.6, on the 77 days both cities were measured. Mecca had the dirtier air on 65 of those days, Helena Valley West Central on 11. Mecca was over the WHO's daily guideline of 15 µg/m³ on 25 of them, Helena Valley West Central on 0.
Right now
The last year, day by day
Month by month
Each city's worst days
Helena Valley West Central
- 10 Apr 2026519.1 µg/m³
- 3 Oct 2026427.6 µg/m³
- 12 May 2026417.4 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
Helena Valley West Central
Side by side with Butte (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, Helena Valley West Central and Mecca, 7 Oct 2025 – 6 Oct 2026, smogrank.com/compare/us-helena-valley-west-central/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.