The weather in Istanbul is typically continental; variable depending on seasons and even, from one point of the city to another, if you consider the city is about 100 kilometers long. Generally, we can say that the temperature in Istanbul is very similar to Madrid’s, with more frequent rains. In Istanbul it can snow in January or February and there are high levels of heat and humidity in summer.
Between December and March Istanbul is cold, gray and windy. The average temperature is about 5 C (42 F), but humidity and wind make you feel much colder. Drizzle and snowfall are frequent and the city usually remains buried by snow in some periods, which brings to it a different charm and a magical look, even when the life of the city is then develope in homes and interiors.
Summers, by contrast, can be oppressive. Average temperatures range between 25 and 30 C° (78-88 F) from June to August, sometimes going beyond 35 C° (104F). The heat and humidity can be exhausting during the day, but at sunset, when it begins to refresh, the city once again becomes lovely and its inhabitants populate the cafes on the banks of the Bosphorus and the Golden Horn.
The best time to visit Istanbul is Autumn and specially Spring, when the days are warm and the nights are mild. At these stations, with highly variable temperatures, the city hosts many festivals and outdoor activities.