The Meteorological Agency on Friday forecast heavy snow overnight for regions facing the Sea of Japan.
On Friday morning snow was already falling in northern Japan, including parts of Hokkaido and Tohoku, and was expected in western Japan the same night.
The heaviest snowfall over the 24 hours until 6 a.m. Saturday was forecast at up to 40 cm in Hokuriku and 25 to 30 cm in other areas along the coast.
The government was stepping up monitoring work at the crisis management center of the prime minister's office in case a disaster occurs, said Deputy Chief Cabinet Secretary Hiroshige Seko.
"We want to see as many people as possible thinking about their safety when they go to vote," the government spokesman said.