On the night of Monday, the temperatures also fell below 0 degrees in some areas in the lowlands.
It has not been that cold for a long time. Even in the lowlands, temperatures fell below freezing in places during the night on Monday. In Zurich / Kloten and in Bern, minimum temperatures of -0.3 and -0.4 degrees were measured. It was colder at these measuring stations for the last time at the end of April or beginning of May.
Coldest on the ground
One speaks of air frost when the air temperature drops below 0 degrees. By default, this is measured at a height of two meters. But even where the 2-meter temperatures remained above zero degrees, ground frost was registered widespread during the night on Monday. When the floor radiates heat at night, the lowest layer of air cools down first. It often happens that the air temperature is still above freezing point at two meters, but the temperature on the ground still drops below zero degrees and thus ground frost occurs.
Protect sensitive plants
If you have sensitive plants in the garden or on the balcony, you should protect them with ground frost during a night. In the case of potted plants, it is advisable to take them in or at least place them on a house wall. If this is not possible, sensitive plants can also be covered with a fleece.