Moscow authorities were rushing to clean the streets after a record-breaking snowstorm descended on the Russian capital. Officials said that schools will stay open on Monday, although going to school was "optional."

The sudden winter storm hit the Russian capital on Sunday, blanketing the city with 43 centimeters (17 inches) of snow within 24 hours. By Monday morning, snow was 55 centimeters thick. The city's famous St. Basil's Cathedral in Red Square was also surrounded by piles of snow.

A sheet of freezing rain coupled with thick, heavy snow weighed down the boughs of trees across the city. At least 2,000 trees have collapsed due to the weight of the snow so far.

Clogged streets and tram rails caused major delays for travelers. Officials warned drivers to avoid the roads if at all possible. Weather experts warn more icy weather and snowfall is on the way.

Around 100 flights from Moscow were delayed due to the storm on Monday alone, according to a service provided by Russian search engine Yandex. Authorities said that 25 incoming flights were also redirected to other airports since weather conditions turned for the worse.

Nearly 70,000 city workers were mobilized across the city to remove snow from the roads. The snowplow pictured above is working to clear tram tracks.

Not all heeded warnings to stay indoors. Some in Moscow took advantage of the heavy snow to go cross-country skiing and sledding in the city's parks.

The weather also left some 60,000 housholds without power in towns around Moscow, although the power was eventually restored. Snow-cleaning crews were doing double their normal runs through the city as temperatures were expected to plunge once again.

At minus 30 degrees Celsius (minus 22 degrees Fahrenheit), these enthusiasts of winter swimming in Siberia don't seem to mind the cold. Running through the snow, they celebrate the beginning of the winter swimming season in Russia.

Two-year-old Alisa and seven-year-old Liza have to get used to the tradition of winter swimming. In recent years, more than 30,000 people took the plunge in Moscow.

No, he is not sitting in a hot bath tub, even though he looks just as relaxed. This man in Novosibirsk seems to enjoy the freezing cold. While most people would fear a heart attack caused by the shock, or at least catching a cold, ice swimming devotees are convinced of its rejuvenating properties.

Russian ice swimmers call themselves "morzhi," which means walruses. They meet every week at their local Walrus Club to dip into the cold water - without any thermal protection, just in regular summer swimsuits.

In Novosibirsk, these ice swimmers venture into a water reservoir. One woman reports: "It was like being pricked by a thousand needles at once."

The most popular form of ice swimming in Russia is religious ice baptism. A cross-shaped hole is cut into the ice. Russian Orthodox Christians celebrate the religious holiday of Epiphany on January 19. According to their tradition, water becomes holy on this day: Believers hope to wash away their sins.

Before the October Revolution of 1917, only a few people would swim in frosty waters regularly. The numbers of ice swimming enthusiasts have only increased after the end of the Soviet Union, when the ritual became very popular. That's when religion made a comeback, although the tradition is not officially endorsed by the Orthodox Church.

Ice swimming can be extremely dangerous unless you are a very experienced "walrus". Because body heat can be lost 25 times faster in water than in air, more than three minutes spent in the cold water might lead to a loss of consciousness and could even be life-threatening.