Japanese weather officials say an extremely powerful cold air mass will bring snow to wide areas, including central Tokyo.
The Meteorological Agency says the air mass with a temperature of minus 24 degrees Celsius covered the northern prefecture of Hokkaido and nearby regions on Friday.
The agency says the air mass is the coldest since related record-keeping began in 1957.
Temperatures remained below minus 10 degrees in Hokkaido's capital Sapporo and Asahikawa City.
The agency says the frigid weather is likely to continue for about a week.
It forecasts up to 10 centimeters of snow in mountainous and flat areas near Tokyo by late Saturday afternoon, and up to five centimeters in central Tokyo.
The agency says more snow could fall by Saturday night, and is urging people to stay alert for frozen roads and traffic disruptions.
Weather officials are urging drivers to ensure that their vehicles have winter tires or tire chains.