Tucumán has a humid subtropical climate, hot and wet in summer (December to March) with afternoon thunderstorms common, and mild and dry in winter (June to August). The best months for visitors are April, May, September, and October, when temperatures are warm but not punishing and rainfall is low.
The big annual event is 9 July, Argentine Independence Day, when Tucumán is the country's symbolic capital. The president traditionally addresses the nation from the Casa Histórica, parades fill the streets, and hotel prices spike — book well in advance if you want to be in the city. Carnival in February is more low-key here than in northeastern Argentina but still worth catching.