You see quite a rise in the summer temperatures in Florence, although the night temperatures moderate a bit. 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 early 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.
In July and August, the streets of Florence will reflect the heat, and Florentines will head out to the hills and lakes. Fiesole is a popular destination, as it sits on a hill where, if the skies are clear, you can peer down upon Florence.
Florence can get crammed with tourists in the summer. In 2011 a record 12 million hotel rooms were filled. That's a lot of rooms. That's a lot of congestion in the streets.
For my money, I'd rather rent a place outside the city, and take public transportation into Florence when I wanted to visit its vaunted museums and attractions. An alternative is to rent an apartment in the city that you'll feel comfortable relaxing in after a long day's sightseeing. VRBO offers a selection of over 7000 properties in Tuscany, over 1,00 in the vicinity of Florence.
That's not to say there aren't great places to stay in Florence inside the city if you're willing to reserve your summer rooms in advance. If you arrive by train, the Grand Hotel Minerva is a reasonable choice. It has a rooftop swimming pool for those hot summer days in July and August when you want to cool off with the domes of Firenze right at eye level.
If elegance is what you seek, take a look at Palazzo Tolomei, a 16th century mansion restored and turned into a highly popular hotel.
Less expensive and centrally located is the B&B Repubblica, highly rated by visitors.
To give you the experience of living like a native, you might wish to check the apartments available in the city: Only Apartments Florence.
It may be enough for you to walk around the art city on your own to take in the Renaissance spirit, ducking into interesting churches for your dose of free art. But if you're there for a while, you'll want to do something special, and we've listed some of our favorite tours, walks and rides that bring out the spirit of life in Florence. See: Florence Tours.
Of course, Florence is in Tuscany, and there are many places to go in the Tuscany countryside after you've seen the sites in the city. See our Tuscany Guide to get information on Italy's largest region.
Florence Guide with a map showing Tourist Attractions and Recommended Hotels, and shopping and eating recommendations.
Museum Tickets - Buy them online to avoid the lines in places like the Uffizi and Accademia.
Florence, Italy Tours - not just your ordinary, umbrella toting guides for these tours; you might actually learn something useful, or do something you've wanted to do, like see Florence while gliding around in a Segway.