You see quite a rise in the summer temperatures in Florence. Florentines head for the hills (Fiesole) or Tuscan beaches on the dog days of summer.
The best times of the year to go to Florence are from late April through early June. Like Rome, late September and October are the best times to go in fall, although you can expect about 9 days of rain in October. Still, it's the time of wine harvest festivals and the start of the winter white Truffle season is usually early November, so you can't be afraid of a little drizzle.
Florence Map showing Tourist Attractions and Recommended Hotels
Florence, Italy Travel Essentials
Top Ten Things to Do in Florence
Florence Hotels - FlorenceBy.Com
Florence Museum Tickets (Reserve online, avoid the long lines)