Russian meteorologists recorded the mildest temperatures for 113 years in the capital Moscow, registering 4.1 Celsius (39.4 Fahrenheit) on Tuesday.
"At 1:00 am (2100 GMT Monday), a temperature of 4.1 degrees Celsius was recorded Tuesday, beating the 1898 record of 3.3 degrees in December," in Moscow, a spokeswoman for the city's weather centre told AFP.
"In the morning, the temperature dropped slightly, but we forecast between three and four degrees in the day...," she added, and it was entirely possible that the record would be broken again in Moscow.
The average temperature in Moscow for the month of December was minus 7.4 degrees Celsius, the spokeswoman added.
Torrential rain in Moscow on Monday evening have combined with melting snow to produce huge puddles in the streets of the capital.