Ile Saint Louis has a fairly mild climate year-round; summer temperatures average around 68 degrees Fahrenheit, while winter temperatures routinely hover around 40 degrees Fahrenheit. Things to Do The atmosphere of Ile Saint Louis is one of the main attractions, so make sure you allot time to stroll the streets, grab a croquet-monsieur, and sip an espresso in a sidewalk cafe. For some fun street entertainment, head over to the Pont Saint-Louis to see who's performing.