Via Nazionale 15 day forecast
The 15 day forecast is calculated with an ensemble forecast that gives the probability of events. The daily temperature and amount of precipitation are shown as a range of 80% likelihood. There is a 10% chance that the actual temperature or amount of precipitation is lower than the probability range, and a 10% chance that it is higher.
In the temperature chart the light shading shows the 80% probability range, and the darker shading shows the 50% probability range. The curve in the middle of the darker area is the median temperature, which is the most probable temperature.