June - September
The most-crowded, sweatiest, hottest and priciest time to be in Rome doesn’t dissuade the hordes of people who descend on Rome during the warmest time of year. Unfortunately for those with children, the best time to visit Rome happens to be during these sweltering summer months. That said, Rome has a canny way of absorbing large crowds, so it never feels overwhelmingly packed with tourists (unless you’re trying to find a place to enjoy your gelato on the Spanish Steps in midday). Like most European capitals, Rome’s denizens often flee for the sea and the mountains during the hot month of August.
October - March
Beautiful, empty Rome. If you want to enjoy this amazing city in its natural splendor, this is the best time to visit Rome. The winter months still boast bearable Rome weather in the Italian capital, but with less than half the tourists who might stalk the city’s streets during the peak season. Best of all, businesses such as hotels and restaurants do not shut down in Rome during the off-season, which means there are plenty of vacancies and available tables and less distance between you and the locals.
April - May
If you're deciding when to go to Rome, travel in the shoulder season may present the best of both worlds: fewer tourists than in peak season, yet better weather than in the off-season. This all conspires to make spring the best time to visit Rome. Hotel prices usually increase toward the end of May, so shoulder season visitors can save a few euros by coming this time of year.