Heavy snow has paralyzed parts of traffic and public life in Turkey.
For Friday, the airlines Pegasus and Turkish Airlines canceled several hundred connections from the two airports in Istanbul, and several connections are also said to be canceled on Saturday.
Classes are also canceled in many parts of Turkey.
Heavy snowfall is also forecast for many places in Greece on Friday and Saturday.
A dense blanket of snow lay on the roofs of Istanbul on Friday morning, and people trudged through gray mud on central Taksim Square.
Mopeds and scooters are not allowed to be on the road, as the governor of the Istanbul province announced.
The passage through the Bosphorus Strait was prohibited on Thursday due to the weather conditions.
The Mayor of Istanbul, Ekrem Imamoglu, called on people to stay at home if possible.
The heaviest snowfall is not expected until Saturday.
Snow probably also on the Peloponnese peninsula
Schools, universities, childcare and other facilities are to remain closed until Monday on the instructions of the Istanbul Provincial Governorate.
The snow does not only hit the 16 million metropolis.
In places on the Black Sea, in parts of eastern and western Turkey, schools will remain closed for the time being, as reported by broadcaster CNN Türk.
According to the weather service, it snowed in Greece at the weekend in northern Athens as well as on the Cyclades islands and even on Crete.
Snow is also expected on the Peloponnese peninsula.
Snow chains are compulsory in many regions and are strictly controlled.
Just a few weeks ago, surprisingly heavy snowfall caused traffic chaos in both countries, and several thousand people were stuck in their cars on the freeways overnight.