The best time to visit Italy is in either spring, early summer, or fall, when the weather is pleasant and the crowds are thinner. May, early June, and late September are particularly good months to visit, as kids are still in school and the weather is glorious. Late June through August is the busiest tourist season. Expect large crowds, with daytime temperatures in Rome, Naples, and Sicily occasionally exceeding 100 and nighttime temperatures exceeding 90. Generally, temperatures are hotter the further south you travel in Italy.  An important thing to be aware of: many tourist attractions and accommodations are closed during the winter months, so if you plan to visit at this time, you will have fewer options. There are also fewer direct flights from the USA during the winter.