Sunny, nice and warm weather without being too much humid is characteristic for Barcelona in September. Light rain from 40mm across nine days and thunderstorms are usual to happen, but it does not last for longer than a day. The daylight during September decreases to less than 12 hours with 9 sunshine hours. Northwestern winds appear with approximate speed of 14 mph. The seawater temperature is the warmest in September from 24°C to 26°C. The average day temperature is from 26°C to 28°C, which does not drop more than 17°C during the nights. Fashion shows during the whole month will take place in Barcelona as well as the International Boat Show, and two national holidays (Catalan National day and La Diada).
The advantage of traveling to Barcelona in September is having the best weather conditions. The weather is warm but not extremely hot, it is pleasant to walk around and you can enjoy the beach and water sports at their most. It is recommended to visit Barcelona in September for a mix of relaxed beach atmosphere and lively town exploration.