The strange snow that fell on a sunny day

“Has it snowed in Gallarate?” Many were wondering this on Monday evening, at least those who were walking around the streets; here and there, depending on the time, the areas between the hills and the plain saw trees, streets and cars covered with a thin blanket of snow. It wasn’t ice, but snow, on which pedestrians left clear footprints, and cars left clear tyre marks.

We received the first report at about 7 p.m., from the hilly area of Cardano al Campo. “It’s snowing.” But there was no sign of snow in Gallarate. Many people joked about it on our Facebook page. At midnight the scene was quite different; in many suburban areas, with the great cold during the night, a genuine, thin blanket of snow also appeared.

Large, visible flakes (as you can see in the picture of a parked car, in Sciarè), which were unmistakeable for the ice of night frost. For example, on Monday evening, the phenomenon was very clear to anyone driving on Freeway 336 Busto-Malpensa-Novara; far away from the built-up areas and warmth, in the Malpensa plain, which is notoriously very cold, the streets were covered with a blanket of snow which had fallen on a sunny day, as the picture sent in by one of our readers shows.

“The phenomenon appears in the areas where there is a lot of humidity, where the fog stagnates and it’s really cold,” the Sub-Alpine Geophysics Centre explained. The humidity takes the form of snow crystals and settles on the ground, as real snow, quite different from ice and frost.

The phenomenon is more similar to soft rime. On a clear day (and night) like that of Monday, the strange “snow” appeared in the lake areas and on the plain, where fog also forms, and where the temperatures are very severe (during the night, – 6° C, in Malpensa, – 7°, in Tradate). The temperature differences between the built-up areas and the countryside or suburban areas, meant that on Monday evening, it was more visible in these areas, which really seemed to turn white from a very light snowfall, which could also be seen, for example, by looking at the streetlamps, which lit up the flakes as they fell, albeit very thinly, from the sky. This may also caused have the localised effect which has been seen in the Gallarate area, and in Milan over the last two days (sleet in Corsico, sun in Porta Genova). Also this morning, on Tuesday, the phenomenon can be seen in the suburban areas (see photo, left: the roundabout at the exit of the 336, Cardano industrial area, on the border of Gallarate).

According to the Geophysics Centre, the phenomenon is certainly not due to pollution, which would occur in the big cities.