There is no single "right" season for Italy: there are ten different Italys, each with its own calendar. The right question is not "when to go", but "which Italy do you want".
Spring (April-June)
The golden season for the art cities: Rome, Florence and Venice with long light and perfect temperatures. The Val d'Orcia is a painting, the Amalfi Coast opens its trails. Beware Easter and public-holiday weekends: book ahead.
Summer (July-August)
The sea at its best — and the art cities at their worst: intense heat and queues. This is the moment for Puglia, Sardinia, Sicily and the Dolomites, where mountain huts open and the passes fill with cyclists. Mid-August (Ferragosto) is Italy at its truest: village festivals everywhere.
Autumn (September-November)
The connoisseur's secret season: grape harvest in the Langhe and Chianti, truffles in Alba, foliage in Trentino, and the southern sea still warm into October. September is arguably the single best month to visit Italy.
Winter (December-March)
Christmas markets in South Tyrol, skiing in the Alps, thermal baths, and the art cities without crowds: the Uffizi in January is a completely different experience. Carnival lights up Venice and Viareggio.
On every BigItalia page you will find the events and seasonality of each territory: build your trip around the right moment.