You should as much attention to the dew point (or relative humidity) as to the temperature. Ice will not form if there is no precipitation in the form of dew, mist or rain.
Here in the United States I follow the website wunderground.com, because it shows temperature AND dewpoint in three-hourly increments. This is most helpful information. I see that it provides weather for Italy too :-)
Dire "ciao" a La Bella Italia per me ... e' stato molti anni fa, quando ho vissuto...
I will salute Italy for you, julianop
![Smiley :)](http://zggtr.org/Smileys/default/smiley.gif)
Anyway, yes, dew point is more precise, but when riding the temperature and the dew point can vary from a curve to another.
Tonight I passed in a long straight at 0°C but right after it was 1 or 2°C. And when arrived at home, just 1 km away, it was 4°C!
Shade, wind, water and other factors can help forming a thin ice layer: when you are at around 0°C it's better to be careful anyway
![Wink ;)](http://zggtr.org/Smileys/default/wink.gif)