Yoshihide Suga announces one-month emergency in Tokyo and surrounding areas, but experts say the measure is inadequate.
At least one person has been killed and 17 wounded in a massive pile-up of at least 134 vehicles in blizzard conditions on a highway in northern Japan, according to officials.
About 200 people were stranded in the pile-up, which forced the closure of the Tohoku Expressway in Miyagi prefecture, the Fire and Disaster Management Agency said on Tuesday.
Chief Cabinet Secretary Katsunobu Kato said a truck rammed into a passenger car, triggering the pile-up over a 1km (0.6 mile) stretch of the highway.
One person was killed, he said.
The disaster agency later said 17 others were injured, including two seriously.
Public broadcaster NHK said it took about eight hours for highway authorities to finish cleaning up the debris.
Traffic authorities had imposed a 50km (30 miles) per hour speed limit at the time of the accident because of low visibility due to a snowstorm, Kato said.
Parts of northern Japan have been struck by heavy snow in recent weeks.
Last year around this time, heavy snow left at least 53 people dead and 574 injured in western and northern Japan.
The loss of life largely occurred in five prefectures along the Sea of Japan in the Tohoku and Hokkaido regions.