Istanbul in September keeps the summer warmth and drops much of the crowd. Average highs are 25.9°C (79°F), the Sea of Marmara still averages 22.3°C (72°F), and the sun sets about an hour earlier than in July. It is the month many travellers pick when they want a swim and fewer queues. Rain returns slowly, with about 5.5 rainy days.
Checked on 10 November 2026. Averages for air come from MGM (1950–2025), and for the sea from the MGM Marmara sea report. Visitor counts come from the provincial tourism directorate. We calculated daylight ourselves for 2027.
Istanbul in September: weather, sea and daylight
| Long-term average | September |
|---|---|
| Daytime high | 25.9°C (79°F) |
| Night low | 17.6°C (64°F) |
| Rainy days | 5.5 |
| Monthly rain | 39.7 mm |
| Warmest day on record | 39.6°C (103°F) |
| Coldest day on record | 7.7°C (46°F) |
| Sea of Marmara, average water temperature | 22.3°C (72°F) |
The water figure is the 1970–2025 monthly average for the whole Sea of Marmara, not for the Bosphorus or the Black Sea beaches, so a local beach can feel colder.
The days shorten quickly. On 1 September 2027 the sun rises near 06:30 and sets near 19:39. By 15 September it sets near 19:16, and daylight lasts 12h32m. Plan evening ferries for before 19:00.
How busy is Istanbul in September?
| Foreign visitors to Istanbul | Number |
|---|---|
| September 2024 | 1,753,540 |
| September 2025 | 1,790,651 (+2.1% on 2024) |
September 2025 saw 1.79 million visitors, about 3% fewer than August 2025’s 1.85 million. The difference is small, so do not expect a quiet city, only a calmer one. For a quieter month, see Istanbul in November.
Istanbul in September: daylight through the month
| 2027 | Sunrise | Sunset | Daylight |
|---|---|---|---|
| 1 Sep | 06:30 | 19:39 | 13h09m |
| 15 Sep | 06:43 | 19:16 | 12h32m |
| 30 Sep | 06:58 | 18:50 | 11h52m |
September loses about 1 hour 17 minutes of daylight, one of the fastest losses of the year. The sun sets before 19:00 from the last week.
September compared with August
| Long-term average | August | September |
|---|---|---|
| Daytime high | 29.7°C | 25.9°C |
| Rainy days | 3.6 | 5.5 |
| Monthly rain | 23.9 mm | 39.7 mm |
| Sea of Marmara | 24.2°C | 22.3°C |
The average high falls 3.8°C, and monthly rain rises by about two thirds. The sea loses 1.9°C, so it stays swimmable early in the month.
What changes in September
- Weather: Mornings and nights cool down. A light jacket helps from the middle of the month.
- Sea: The water is at its best for swimming in early September, just after the hot summer.
- Prices: Hotels often fall from their summer peak. Compare dates before you book.
- Day length: You lose about two and a half hours of daylight between mid-June and mid-September.
What to do in Istanbul in September
Choose longer walks and day trips. Our day trips guide lists options without a car. The old city is easier to enjoy at 09:00 than in July. Our Balat and Fener walking guide and Kadıköy market guide suit warm autumn light.
Per day, the official count gives about 59,690 foreign arrivals in September 2025, almost the same as August 2025 at about 59,770. This is our own division. Crowd levels look similar to August, so the change you feel is mostly the cooler weather.
A September plan for cooler days
Do your longest walk in the morning, then take a day trip on a dry day. Pick one from our day trips guide, and check the ferry timetable the evening before. Put a covered visit on the rainy afternoon. Our rainy day guide has options. Use the Kadıköy food market guide for a food day.
Packing list for a September trip
- Summer clothes for the day and a light jacket for the evening.
- A compact rain shell for the first autumn showers.
- Swimwear for the early part of the month.
- Sun cream, since midday sun is still strong.
Should you visit Istanbul in September?
Yes. It joins warm weather, a warm sea and slightly thinner crowds. Pair it with May as the two best months. Our weather table shows both side by side.
September questions answered
Is the sea still warm?
Yes. The Sea of Marmara averages 22.3°C, according to MGM.
Are hotels cheaper than in August?
Often a little, but demand is still high. Compare several dates.
