On Average:
July is the warmest month.
January is the coolest month.
November is the wettest month.
July is the driest month.

The most popular time to visit Rome from a weather perspective is during the height of summer and periodically in winter. If you don’t like crowds, don’t go during Easter, May, September, or Christmas. Tourism is the most popular in July and August, so make plans early for hotel rooms and know that space in every cathedral and museum will be at a minimum. Hotels are more expensive during the high season because of all the tour groups visiting. The locals manage the crowds by avoiding this frenzy for their own trips, especially around August 15, on the holiday known as Ferragosto. Easter, of course, is completely overrun with tourists making a pilgrimage to the holiest of places.

The best weather and conditions in Rome however, are in mid-spring or fall, when the weather is temperate, the hotel prices are more affordable, and tourists are at a minimum. At this time, you can attend the gorgeous autumnal olive and wine harvests in Lazio and the springtime flower shows in the city. Even though the weather is temperate, everyone seems to migrate indoors at this time of year.