According to the folk calendar - Kirill - Deri Poloz

Orthodox believers on this day honor the memory of St. Cyril of Jerusalem, archbishop of the 4th century. The holiday is named after him. On St. Cyril's Day, the days in the southern regions were often fine, but in the northern regions there could still be snow. During the day it melted, and at night frosts struck, and if the owners carelessly left the sleigh in a mess of earth and snow, then in the morning they had to literally tear up the runners of the sleigh. Because of this, the people nicknamed the date Deri Snake.