Jacaranda trees are native to Brazil. As such they should be considered a subtropical species. Here on the Central Coast, although they survive and some even flourish, they should be considered as being on the edge of their range. My references say that mature trees will survive a freeze as low as 25°F, but young trees will not survive, and mature trees will probably sustain some freezing injury at temperatures between 25° and 30°F, depending on the duration of the frost. Also in our Central Coast climate, jacarandas do not flower if exposed directly to frequent ocean winds. They also will not flower or flower poorly where they do not get adequate heat.
So, if you want a jacaranda, plant it in a place where it is protected from the west winds, and where it will get as much sunshine and heat as possible.