Russia is the largest country in the world by area. The country covers around one-eighth on the land. The climate of Russia is produced under the pressure of several determining factors. The mammoth size of the country and the seclusion of many areas from the sea result in the supremacy of the continental climate. Such climate is prevalent in European and Asian Russia except for the tundra and the extreme southeast. Mountains in the south obstructing the flow of warm air masses from the Indian Ocean and the plain of the west and north makes the country open to Arctic and Atlantic influences.
Due to the temperate control of the Atlantic or Pacific, most areas of Russia in European Russia, in the south of West Siberia and in the south of the Russian Far East, including the cities of Moscow and Saint Petersburg, practice a humid continental climate. Most of Northern European Russia and Siberia between the Scandinavian Peninsula and the Pacific Ocean has a subarctic climate, with extremely severe winters in the inner regions of Northeast Siberia and more moderate everywhere else.