Brasilia has a tropical savanna climate (Aw) according to the Koppen system, with two distinct seasons: the rainy season, from October to April, and a dry season, from May to September. The average temperature is 20.6 C (69.1 F). September, at the end of the dry season, has the highest average maximum temperature, 28.3 C (82.9 F), has major and minor lower maximum average temperature, of 25.1 C (77.2 F) and 12.9 C (55.2 F), respectively. Average temperatures from September through March are a consistent 22 C (72 F). With 247.4 mm (9.7 in), January is the month with the highest rainfall of the year, while June is the lowest, with only 8.7 mm (0.3 in).

Answer this question, if possible (if impossible, reply "unanswerable"): When is Brasilia's rainy season?
October to April