Snow is referred to rain and snow (also sleet) when it consists of a mix of rain and snow. According to the expected development of the temperature sleet is more or less dangerous for traffic. It happens when there is precipitation when it is freezing, when the bigger snow flakes don’t melt, while the smaller flakes start melting in the air while they are falling down to the earth. If the ground is frozen, sleet can become dangerous black ice. If the ground and air temperature, however, are significantly higher than 0° C, the
probability is high that streets will be very slippery. It is also likely to happen when the precipitation occurs during the warm fronts, when there is a gradual transition from snow to rain.

When there is precipitation and the temperatures are around freezing, matters are complex and depend on the humidity and the temperatures on the ground and in the various atmospheric layers. Accordingly it cannot be predicted what shape precipitation will fall to the ground as. Frequently this also depends on regional conditions. When in doubt one should drive with greater caution when sleet has been predicted for a certain area. Even when snow has been forecasted and it only comes down as sleet one should not be deceived by it and should drive carefully, as certain patches can remain extremely icy and thus dangerous.

Ice rain, unlike sleet, consists of freezing rain drops which are considerably colder than 0° C and which fall to the ground in the shape of drops because of a lack of crystallization nuclei; they freeze on the spot when they hit the ground. Ice pellets and soft hail are also not ice rain, even though they appear to be. Like hail they partially consist of ice crystals which are already hard when they fall to the ground.

They can be mixed with rain but it is still a mixture of rain and ice and not sleet. Sleet is not very welcome in winter sport regions. It brings on a rapid deterioration of the conditions on the ski and sledding slopes and can easily turn into ice over night.

Then winter sport can grind to a halt, becoming restricted and more dangerous. Temperatures permitting and when the prerequisites are given, snow canons are used to cover the slopes with artificial snow to make them usable again. The temperature must be just right to be able to do this. When the temperature goes up and the melting process has started, snow canons are useless.