Weather
Tuscany:
Generally the climate in Umbria and Tuscany is very mild. However, there are small variations between the regions due to the geography of the area. Summers are hotter along the coast and in the valleys than they are in the hills, where the climate is very continental and rain falls more often. The summers in Tuscany are very hot and dry, especially in the valleys. Spring (April and May) and autumn (October and November) are filled with sunny days but the chances of rain are higher.
The busiest time for tourism is August when most Italians are on holiday. Both July and August are very busy but the main tourist season stretches from mid-April to the end of September. The best time to visit Italy is the quieter part of the season, from April to June and from September to October, when the weather is usually good, the prices are lower and there are fewer tourists. Just beware that tourists crowd the major cities at Easter, when Italians flock to resorts and the countryside. The weather is warm enough for beach visits in most of the country from June to September.
Florence:
The best time to visit Florence is in May, early June, late September and October. Days during those months are usually warm, and quite long. Since most Italians leave their hot cities in the summer, many restaurants in Florence are closed.
Rome:
It's warm all over Italy in summer, but it can be very hot in Rome. The high temperatures begin in May, often lasting until sometime in October. In Rome the weather is warm year-round, averaging 50°F (10°C) in winter. For the most part, it's drier in Italy than in North America, so high temperatures don't seem as bad because the humidity is lower. In Rome, temperatures can stay in the 90s for days, but nights are cooler and much more comfortable. The average high temperatures in central Italy and Rome are 82°F (28°C) in June, 87°F (31°C) in July, and 86°F (30°C) in August; the average lows are 63°F (17°C) in June and 67°F (19°C) in July and August.
April to June and late September to October are the best months for traveling in Italy—temperatures are usually mild and the crowds aren't quite so intense. Starting in mid-June, the summer rush really picks up, and from July to mid-September the country teems with visitors. From late October to Easter, most attractions go on shorter winter hours. Many hotels and restaurants take a month or two off between November and February and it can get much colder than you'd expect (it might even snow).