Sometimes the cold returns

Pavel Toropov, associate professor of the department
meteorology and climatology
Faculty of Geography, Moscow State University

– The warm weather that has settled in the European part of Russia is very deceptive. It is not for nothing that there is such a thing as the May return of cold weather. This is what meteorologists call the invasion of cold Arctic air into the temperate latitudes of the European part of Russia and Siberia. The fact is that spring is a contrasting time of year. Summer has already arrived in the subtropics - the height of the sun there is the same as in Moscow in mid-June. At the same time, spring has not yet begun in the Arctic - below the Arctic Circle, negative temperatures remain almost everywhere, even during the day.
Warming in the European territory of Russia is associated with southern cyclones that move through Ukraine and Belarus. Most of the European territory ends up on the eastern periphery of these vortices. They supply warm air to the Volga region and the middle zone. If cyclones passed through the Urals and the Volga region, then the Moscow region would be overwhelmed by cold weather, because winds from the Arctic Ocean would prevail. In April-May, when the Arctic has not yet awakened, they bring a drop in temperature.
Returns of cold weather are a phenomenon that repeats from year to year, and therefore people gave them conventional names. The cold in the first ten days of May was called bird cherry, in mid-May - oak, the last wave was called sheep - on the eve of summer, sheep were sheared, the unfortunate animals were shivering from the cold. But these three waves of cold weather are just as conventional as, for example, Epiphany frosts. That is, they may come, or they may not take place. In 2007, for example, the entire month of May was abnormally warm, and in 2000 the cold lasted for two weeks. It is impossible to predict the return of cold weather earlier than one week in advance.
Grain and fruit crops suffer from low temperatures in spring. Sometimes, due to the return of cold weather, some grain crops are replanted in the Black Earth Region. On a small plot of land you can protect yourself from the cold. It is necessary to light fires, creating a high smoke screen - it prevents the soil surface from cooling. Plants and animals are better adapted to the return of cold weather.