Île Saint-Louis is a five-minute walk in any direction, which means every choice you make about which quay matters more than usual. The north (Quai d’Anjou) takes the building shade most of the morning; the south (Quai de Béthune) flips by 3. The east end is open to the river; the west end is where the islanders live and the planes work overtime.
Tap any pick — Stay Cool re-shades it against the current sun. If it’s 6 PM and you’re going to Berthillon, the app moves you to Quai d’Orléans automatically.