There is no best time as such to visit Curitiba. It is never hoarded with tourists and the weather is quite pleasant all year round. Although the winters get really chilly; the tropical climate is sure to be different for you than the usual four seasoned climate. It also lies in a temperate zone and hence the weather is somewhat like this. There is no defined Summer and Winter. Precipitation can happen at any time of the year and the last snowfall was in the year 2013.