São Paulo sits on a 760-metre plateau, which keeps it cooler than the Brazilian coast. April to October is the best stretch: dry, sunny days in the mid-twenties, cool evenings. November to March is the wet season, with hot, humid afternoons that often end in spectacular thunderstorms; the city can flood and traffic can be miserable.
The São Paulo Carnival in February or early March is smaller and more local than Rio's, but the blocos (street parades) have grown over the last decade and the Anhembi Sambódromo runs serious parade nights. The Virada Cultural in late May is a 24-hour citywide cultural marathon with free concerts and performances on every plaza. The São Paulo Bienal runs from September to December in even-numbered years — the second-oldest contemporary-art biennial in the world after Venice.
Hotel rates are highest during Formula One weekend (November) and the big international art and design fairs.