Rome has one of the most optimal number of hours of daylight in Europe. Days in winter are not as short as in the northern part of the continent, the average hours of daylight in December, January and February is 10 hours (for comparison: London or Moscow or Warsaw – about 8 hours).
Rome’s coldest months are January and February. During these two months, it rains every couple of days but some days can be quite pleasant with high temperatures of 12°C (53°F). Snow is very rare in Rome (once every 10 years or 15 years).
The wettest month in Rome is December, and on average, autumn and winter precipitation levels are higher than in London.
Rome averages 62 days a year with temperatures of 30°C or more (86 °F). The weather gets that hot on most summer days and shows up periodically during May and September. The hottest days in June and July reach into the high 30°C (over 100 °F). The discomfort from heat and humidity is highest during the months of July and August.
Until the middle of October it's usually still "dry" while the end of October and November sees the beginning of winter rains and chillier temperatures. Sunny cloudless skies are still common.
Spring and Autumn for most are the best time in Rome. The average daytime temperatures in April are at around 20°C (68°F). By June these will rise to a very pleasant 29°C (80°F) during the day and at night an average of 15°C (59°F).