The record-breaking heatwave is forcing authorities to take emergency measures.
Geneva has ordered all outdoor work in direct sunshine to stop from one o'clock each afternoon until Sunday, as temperatures climb towards 36.
Essential workers such as airport staff, traffic officers and lifeguards are exempt but must follow strict work-and-rest cycles.
The heat has already broken Switzerland's all-time June temperature record, with Basel-Binningen reaching 38 degrees.
Much of the country remains under the highest Level 4 heat warning, while Valais has imposed a total ban on outdoor fires because of an extreme wildfire risk.
The hot weather is expected to continue until at least Monday.
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