People who have to drive to work in particular fear warnings of freezing rain and lightning ice on frosty days. The result is slippery roads and an increased risk of accidents. Anyone traveling by bike or on foot also needs to be particularly careful.
But what exactly is freezing rain? According to the German Weather Service (DWD), freezing rain is, on the one hand, “supercooled rain that immediately freezes into ice when it hits solid objects and covers the objects with a layer of ice.” Something similar can be read on the “Wetter.de” portal. “It says: Freezing rain is a form of frozen rain that freezes instantly upon impact with the earth.” If this freezing precipitation hits streets and sidewalks, they suddenly become slippery – this circumstance is also the background of the frequently used term “lightning ice”, which, according to the DWD, is not a meteorological term.
Technical term or not: The name is pretty accurate. And it is precisely this immediate ice that poses a danger to drivers, cyclists and pedestrians. If they are surprised by freezing rain and lightning ice, there is a risk of falls and accidents. Vehicles slide uncontrollably on the road, feet slip away, physical rules seem to be suspended.
The ADAC even recommends taking a break in the event of lightning ice and waiting for the road service, as the tire grip is virtually zero (you can read more about this here). The bike should also be left standing and pedestrians should – if avoidable – not go outside until sidewalks have been gritted or the ice has melted. Otherwise there is an acute risk of injury.
Freezing rain can also occur when the precipitation freezes in the air and the drops form ice grains.
The DWD also makes a distinction between the different types of smoothness.
Slippery ice is caused by frozen meltwater or puddles on roads and asphalt paths. Since rain doesn’t necessarily have to fall beforehand, ice can occur without any apparent warning.
Black ice, in turn, is caused by the spontaneous freezing of rain described above. Black ice can also occur briefly when raindrops are not supercooled but hit icy ground.
On the other hand, we are talking about slippery frost when morning frost on sidewalks and streets is compressed by shoes or tires and becomes a smooth surface through liquefaction and refreezing.
Slippery snow, in turn, is caused by a compressed layer of snow on roads and paths. As with frost, the surface briefly liquefies due to the pressure and then freezes again.
Sources: Wetter.de, DWD
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