Spain's weather in September is generally warm and pleasant, with countrywide temperatures averaging around 77-82°F (25-28°C) during the day and dropping to around 68-72°F (20-22°C) at night. In the north of the country you should expect temperature ranges of 60-80°F, while the south will be hotter, around 70-90°F.

The south of Spain (Andalusia) remains quite hot in September, with average daytime highs ranging from 28°C to 32°C (82°F to 90°F). In inland cities like Seville and Córdoba, temperatures frequently spike to 35°C (95°F) during the first half of the month, as the region retains much of its summer heat. On the coast, such as in Malaga or Marbella, the Mediterranean breeze keeps things slightly cooler and more humid, typically hovering around 26°C to 28°C. By 2026, climate trends have shown that "late summer" heatwaves are becoming more common in Andalusia, making September feel much like August in other parts of Europe. However, the evenings bring a welcome relief as the sun sets earlier, with temperatures dropping to a comfortable 18°C (64°F). It is one of the best times to visit because the "dry heat" makes sightseeing manageable, and the sea temperature is at its annual warmest, perfect for swimming without the extreme "oven-like" intensity of July.