إسطنبول في سبتمبر: الطقس وحرارة البحر والفعاليات

September is warm, mostly dry and still a swimming month in Istanbul. Daytime highs average about 26°C and nights about 18°C, with rain on only five or six days. The Sea of Marmara averages 22°C, barely two degrees below August. For many travellers it is the best month of the year: the heat of July and August has eased, the sea is still warm, and the city's own summer holiday traffic drops when Turkish schools go back in mid-September. You can spend the morning on the Old City sights and the afternoon on the water without either feeling like hard work. A good way to start is a morning highlights tour of the Old City, which finishes before the hottest part of the day.

September weather and sea temperature

MGM, the Turkish State Meteorological Service, publishes long-term averages for the Istanbul station (1950 to 2025) and monthly sea temperatures for the Sea of Marmara (1970 to 2025). This is how September compares with the months either side:

The sea has been warmer than the long-term figure in recent years. MGM measured a September average of 24.9°C in 2024. The early part of the month usually still feels like summer, while the last week brings cooler evenings and sometimes the first autumn storm.

Daylight shrinks quickly. In Sultanahmet, the sun sets at about 19:37 on 1 September, 19:14 on 15 September and 18:48 on 30 September. Sunrise moves from 06:31 to 06:59. Türkiye stays on UTC+3 all year, so the clocks do not change.

Where to swim in September

Istanbul has two seas, and they feel very different:

• The Black Sea coast at Şile and Kilyos has long sandy beaches and open water. It also has strong waves and dangerous currents on windy days. Swim only at beaches with lifeguards, follow the flag system, and stay out of the water when the red flag is up.
• The Sea of Marmara is calmer. The Princes' Islands have small beach clubs and coves reached by boat or on foot from the ferry piers. It is the easier choice for families with young children.

Şile is roughly a 1.5 to 2-hour drive from Sultanahmet, depending on traffic. Some beach clubs reduce their hours or close by the end of September, so check before you go late in the month. Weekdays are far quieter than weekends.

A private yacht, a sunset Bosphorus yacht cruise or a long Bosphorus cruise is the other way to enjoy the water in September. Some charters on the upper Bosphorus stop for a swim when conditions allow.

Events in September

September is the start of Istanbul's autumn season:

• Contemporary Istanbul. The city's main contemporary art fair, held at Tersane Istanbul on the Golden Horn. The 2026 edition ran from 23 to 27 September.
• Akbank Jazz Festival. It opens in late September and runs into October. In 2026 it began on 26 September.
• Back to school. The Turkish school year started on 14 September in 2026. After that date, weekday traffic is heavier at rush hour, but beaches and attractions are less crowded with domestic visitors.

There are no national or religious public holidays in September 2027. Victory Day on 30 August falls just before the month starts.

Check 2027 dates on the organisers' websites. Art fair and festival dates are usually announced several months in advance.

Sightseeing in September: how to plan the day

The first half of September can still reach 30°C on some afternoons, and the Old City has little shade between the sights. The rhythm that works best:

1. Start at opening time with Hagia Sophia, then the Blue Mosque and the Hippodrome before 11:00.
2. Go underground or indoors at midday. The Basilica Cistern is cool all year, and Topkapı's Harem and treasury rooms are shaded. Topkapı Palace is closed on Tuesdays.
3. Spend the afternoon on the water. A Bosphorus cruise, a ferry to Kadıköy on the Asian side or a boat to the Princes' Islands.
4. Walk after 17:00. Galata, Karaköy and the shore at Ortaköy are at their best in the early evening, with sunset before 19:40.

On Fridays, visit the mosques before the midday prayer, which falls around 13:00 in September. Visitor entry stops for longer then than on other days.

Crowds and prices in September

September is still high season for international visitors. Hotels in Sultanahmet, Karaköy and along the Bosphorus are busy, and cruise ships still call at Galataport. Weekends are the busiest days. Rates generally ease a little after mid-September but stay well above winter levels.

Practical booking advice for the month:

• Reserve hotels and a guide for the Topkapı and Hagia Sophia day a few weeks ahead.
• Book sunset cruises and yacht charters early, because the evenings are the most popular time.
• If you want the beach, go on a weekday and before the last week of the month.

What to pack

Summer clothes for the day, plus one warmer layer for evenings on the water. Bring a swimsuit, sunscreen, a hat and sunglasses. For mosques, men and women need clothing that covers their knees and shoulders, and women need a scarf for their hair. A light shawl or loose trousers in your day bag means you do not have to change your plans. Comfortable shoes with grip matter for the hills of Galata and the marble floors of the Old City.

Tours that cover this

These are the tours we suggest most often in September:

• Old City morning highlights small-group tour, from $120 per person. Hagia Sophia, the Blue Mosque and the Hippodrome before the midday heat.
• Şile Black Sea beach and pool day trip, from $60 per person. A full day on the Black Sea coast with transport from the city.
• Princes' Islands full-day tour with ferry and lunch, from $90 per person. Car-free islands in the Sea of Marmara.
• 2-hour private Bosphorus yacht cruise, from $600 per group. A good choice for a sunset on the water.

Frequently Asked Questions