Further down the Rhone valley Visp broke its all time August record when it hit 35.5 degrees, while Geneva reached 36.5, its hottest day since the heatwave of 2003, said MeteoNews.
Sweltering heat was felt across much of western Switzerland in particular, with temperatures exceeding 33 degrees in Bern, Solothurn, Neuchatel and Nyon, as well as Lugano in the south-eastern canton of Ticino.
Though it was the hottest day of 2017, Thursday was still a far way off beating Switzerland's all-time record, held by the Mesolcina valley in Graubünden which reached 41.5 degrees in 2003.
The high temperatures are set to continue until Saturday, with MeteoSuisse issuing a heatwave alert on Friday for Ticino (level four) and Geneva and parts of the Valais (level three).
Rain and much cooler temperatures will arrive on Sunday.