Among the victims was a 37-year-old man who died on Saturday in Lake Geneva while swimming near the Pâquis outoor baths in Geneva.
Cantonal police said they were alerted to the man’s disappearance late in the afternoon.
His body was discovered by a police diver 3.7 metres beneath the water’s surface.
A 20-year-old woman lost her life the same day while canyoning in the Ragn da Ferrara river in the canton of Graubünden.
The woman became stuck between two rocks in a narrow section of the river canyon where the current was particularly strong, cantonal police said.
A male companion attempted to use a knife to cut the life jacket she was wearing, police said.
However, the woman was dragged by the force of the current under water.
All rescue attempts failed and recovery of the body proved difficult and costly because of the difficult terrain, police said.
In Bern, an 80-year-old man drowned in the Aar River, also on Saturday.
Passersby noticed the man’s body floating in the river around 6pm, Bern cantonal police said.
Rescue officials were unable to resuscitate the man, police said.
Elsewhere, a professional fisherman was found dead in Lake Neuchâtel on Friday near the community of Cheseaux-Noréaz in the canton of Vaud.
Police believe his death was accidental.
On the same day, a 33-year-old Polish man residing in Switzerland drowned while swimming in Lake Thun in the Bernese Oberland, near Oberhofen (canton of Bern).
These incidents followed the death on Thursday of a two-year-old boy after he fell into his family’s swimming pool in Fully, in the canton of Valais.
The boy’s seven-year-old brother, who also fell in the pool, remains in critical condition at Lausanne’s university hospital.
The boys apparently breached a security fence surrounding the pool while their mother was briefly away from the house.
The drownings occurred in the first few days of a heatwave that MeteoSwiss, the national weather office, predicts will continue through the week.
Temperatures as high as 35.5 degrees were recorded in Valais on Sunday and many Swiss regions are expected to see the thermometer rise above 30 degrees for the next five days.