The best website I've found for weather predictions is http://www.meteo.it/. I have found it to be very accurate. Unfortunately, I've been having to use this site much too frequently lately.
-click on the map of Italy on the left side (says ITALIA);
-a window will pop up with a large map of Italy; click on the region you are interested in
-the forecast is presented using the 24 hour clock, it will cycle through this automatically or you can select the 6 hour time you are interested for the current day ("OGGI"). The default display is the weather "TEMPO" but you can also select temperature "TEMPERATURA" or sea and wind conditions "MARE E VENTO".
-you can also select DOMANI to see the weather for tomorrow; in all you can look at 6 days with the last two being long term predictions.