On January 19, the Orthodox Church celebrates Epiphany (Креще́ние), the day when St. John the Baptist baptized Jesus Christ in the River Jordan. On this day, a ceremony of blessing water takes place in every Orthodox Church. It is believed that on this day water becomes holy (святая вода) and has special healing power. For that reason, ice-holes in the form of a cross are made on rivers, lakes and ponds, where many Russians jump into freezing water, washing their sins away. Even though the water is very cold, no one has ever got sick after the ritual. In almanacs, this holiday was tied to heavy frosts, so-called "Epiphany frosts" (креще́нские моро́зы).
Also, some people fill containers with 'holy water' on that day. It's interesting that the water will never go bad.