One person has died and at least 27 have been injured in road accidents across the country since Sunday.
Police reported about 200 accidents due to the icy roads.
The worst mishap occurred just after midnight as a driver lost control of his car near the village of Thunstetten in canton Bern and crashed into a tree. An elderly passenger was killed.
After weeks of freezing temperatures on the north side of the Alps, milder air swept across Switzerland on Sunday, bringing rain.
However, the wet roads froze overnight due to the low ground temperatures.