Rome has a Mediterranean climate. This means Rome has mild winters and hot, dry summers. The warmest months in Rome are July and August where temperatures often reach above 95 degrees fahrenheit. Winter in Rome is very mild, with the average temperature being around 55 degrees fahrenheit in December. Travelers have found that the best time to travel to Rome is between March and May. This is when we see warm weather and blue skies. However, rain can occur at almost anytime in Rome. Whereas, heavy snowfall is rare.
Source: Paulina Pimperova, Rome, WordTravels, http://www.wordtravels.com/Cities/Italy/Rome/Climate (Accessed November 20, 2017).