Istanbul straddles the Bosphorus strait in northwestern Turkey, the waterway dividing Europe from Asia and linking the Black Sea to the Sea of Marmara, at approximately 41.01°N, 28.98°E. It has a transitional climate on the boundary between Mediterranean, humid subtropical and oceanic types — hot, fairly dry summers and cool, wet winters — shaped by the surrounding seas and by its exposure to both Mediterranean and Black Sea weather.

Summer, from June to September, is warm to hot and relatively dry, with July and August the warmest months — average highs around 28–29°C — and often humid thanks to the surrounding water. Hot spells can climb higher, but sea breezes off the Bosphorus and Marmara temper the heat. Rain is much reduced compared with winter, though the city is not as bone-dry in summer as the Mediterranean coasts further south, and occasional showers occur.

Winter, from December to March, is cool, wet and often grey, with January and February the coldest — average highs around 8–10°C and lows near 3–5°C. Cold outbreaks of continental air can bring sharp chills and snowfall, which settles across the city several times most winters, sometimes heavily, while the cold northeasterly Poyraz wind off the Black Sea sharpens the feeling of cold. Rain, wind and damp dominate the season.

Istanbul is fairly wet, receiving around 730–850 mm of rain a year, with a clear autumn-to-winter maximum — December is typically the wettest month — and a drier, though not rainless, summer. A share of the winter total falls as snow. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Istanbul's position between two seas and two air-mass regimes gives it changeable, transitional weather quite unlike the dry Mediterranean south of Turkey: it can see Balkan-style snow in winter and Mediterranean warmth in summer. Local winds off the Black Sea, especially the cold northeasterly Poyraz and the milder southwesterly Lodos, drive many of its day-to-day shifts, and the Bosphorus can occasionally fill with fog that halts shipping.

To follow any single measurement in Istanbul more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.