I found some good things regarding the weather during our stay in Italy. www.weather.com has an excellent site showing the high, low, and averages.
When we're in the Florence/Tuscany area, the average high temperature is 79 degrees and the average low is 57. Another site said the minimum average temperature of 57 was taken at sunrise (www.italyflash.com), and showed the average maximum at 82. This site took the averages from 1992 to 1996. I believe the other site spread the average over 30 years. Either way, we'll probably see warm weather.