Summer (May to end of September): August is the hottest month with temperature exceeding 30 degree Celsius. The humidity reaches its peak and it can get very hot. Also, its labyrinth of ancient streets and attractions can become extremely crowded in high season. This is also the season of festivals and parties!
Autumn (October to late November): Cloudless skies, sunny days and lesser crowds, this is an ideal time to visit Rome. The average temperature is around 18 to 20 degree Celsius.
Winter (November to mid-March): Although snowfall is rare and temperatures rarely fall below 0 degree Celsius, the weather is extremely unpredictable in these months and you might need to pack warm clothing as well as an umbrella. December is a crowded month and the prices of hotels and flights shoot up. The average high temperature in January is about 12.9 °C (55.2 °F). Apart from the the month of December, this is an off season to visit Rome.
Spring (Late March and April): Ideal time to visit Rome except around the Easter Sunday when devotees flock to the Vatican City.
The best time to visit Rome April to June and September, October. The days are sunny and warm with rare rain showers. This is also the shoulder season for visiting Rome. Look at the timings of all attractions for your Rome tours.