The jacaranda — Jacaranda mimosifolia, native to northwest Argentina and southern Bolivia — was planted across central Buenos Aires in the 1930s under the urbanist Carlos Thays as part of his park-and-boulevard plan. The trees flower in early November in this latitude, lavender-blue, and the bloom lasts about three weeks. Week three is the peak; the canopy is at its fullest, the air is starting to warm but hasn’t yet committed to summer, and the petal-fall covers the sidewalks in a soft blue layer that has its own minor effect on the heat budget (high albedo, low thermal mass). The walk to do in this city, in this window, is the Palermo jacaranda walk. After that you wait a year.
The picks below string the densest jacaranda blocks: along Avenida Figueroa Alcorta, around the Plaza Italia traffic circle, through the camellones of Avenida del Libertador, into the Botanic Garden and the Plaza Mitre. Stay Cool grades these for late November sun and the actual canopy density; the bloom map is updated weekly during the season. A practical note: the jacaranda canopy is dense but not as dense as a plane or a fig. The shade scores below are honest, averaging around 80%, and they drop in week four when the petals are down and the leaves are still coming in.
On timing within the day: jacaranda is best photographed in mid-morning, with the sun behind you, when the blue reads true. As shade it works through the early afternoon. After about 4 PM the light goes warm and the canopy stops reading as cool; the routes recompute toward the heavier ombú and tipa shade of the parks.