Montevideo is a year-round destination with a temperate climate — warm and dry summers (December–March), mild and often rainy winters (June–September). The best weather is in autumn (April–May), when temperatures are comfortable and the city is less crowded than in summer.
Carnival (January–February) is the city's great annual event — 40 days of murga performances, candombe drumming, and street processions. The Desfile Inaugural opens the season and the final Saturday parade closes it; both are spectacular. Performances happen throughout the city every night during Carnival.
August is the local equivalent of Carnival-off-season — the city quiets down considerably as Uruguayans leave for the beach at Punta del Este. This is actually a good time to visit if you want a calm experience and lower hotel prices.
Winter (June–September) sees cold nights and some rain, but the city remains fully functional and less touristic. The Rambla is used year-round by locals with their mate flasks, rain or shine.