According to MeteoNews the hottest place in the country was Sitten in the Valais, which reached 31.9 degrees on Sunday.
But the high temperatures were widespread, with parts of Graubünden, Basel-Land, Zurich, Geneva, Glarus and the Jura all surpassing the 30-degree mark.
Though such high temperatures are not a regular occurrence in May, the weekend's mini heatwave was far from being a record.
According to SRF Meteo that was in 2009 when Sion reached 35.5 degree on May 25th.
The heat added to the misery of drivers returning home from southern Switzerland and Italy on Sunday.
Traffic jams of 11km built up at the Gotthard road tunnel on Sunday evening, with travellers having a near three-hour wait to get through it, reported news agencies.
Traffic finally returned to normal around 11pm.
Trains were also disrupted by an accident involving a person at Bern-Wankdorf station on Sunday morning.
Several services that travel through the hub were disrupted during the morning.
The hot weather is expected to persist on Monday before storms arrive later in the week.