Monaco in September offers a transition from the hot summer months to a milder autumn. Typically, daytime temperatures average around 24C (75F), dropping to a comfortable 18C (64F) in the evenings. Sea temperatures remain warm, generally around 22C (72F), making swimming and other water activities still enjoyable. Rainfall is relatively low, with an average of around 70mm spread across the month, meaning sunny days are still prevalent.
This period offers a pleasant climate for visitors. The slightly cooler temperatures make exploring the city, visiting its gardens and attractions, or attending events like the Monaco Yacht Show more comfortable. The reduced crowds compared to the peak summer season allow for a more relaxed experience. Historically, September has marked the end of the traditional tourist season, offering a balance between pleasant weather and fewer visitors.