SmogRank / World / Switzerland / June 2025

Most unhealthy days in Switzerland, June 2025

2 cities in Switzerland ranked by their share of unhealthy days over the 30 days. The most unhealthy days: Winterthur, Switzerland, 1 of 27 measured days. A city needs measurements on 70% of the days to be ranked.

Switzerland has 9 cities ranked over the last 30 days, but only 2 here: most of its monitors have no readings for June 2025 in OpenAQ's archive, where ours come from, or too few to rank. Cities missing from this board weren't clean, just not measured.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

All cities in the world, June 2025 · Switzerland now

Regions

Ranked cities in each region, June 2025.

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SmogRank, most polluted cities in Switzerland, by unhealthy days, PM2.5, June 2025, smogrank.com/ch/history/2025-06?by=days (accessed 10 Oct 2026). Some readings from Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published.

Download top 10 by average (PNG)

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.