Key Facts
• December 31 features a winter pressure pattern with cold air influx.
• Northern Japan’s upper atmosphere (~5000m) sees below -33°C cold air.
• Heavy snow expected mainly on Sea of Japan side in Hokkaido and Tohoku.
• Tohoku may see up to 70 cm snow in mountains, 50 cm in plains by 6 a.m. Jan 1.
• Hokuriku region faces intermittent rain, snow, and thunderstorms with lightning and tornado risk.
• Kanto to Kyushu mostly clear but cold; mountain areas may get snow clouds.
• Okinawa experiences intermittent rain.
• Temperatures drop nationwide on Dec 31 compared to Dec 30.
• Sapporo: -3°C; Sendai: 4°C (8°C lower than previous day).
• Tokyo: 13°C; Osaka: 11°C; Fukuoka: 9°C, all lower than Dec 30.
• North winds make it feel colder than actual temperatures.
• Stronger cold expected through the morning of Jan 1; prepare for New Year outings.
Summary
On December 31, a winter pressure pattern brings cold air southward across Japan, causing heavy snow mainly along the Sea of Japan side in northern regions like Hokkaido and Tohoku. Tohoku faces significant snowfall, with mountain areas possibly receiving up to 70 cm and plains up to 50 cm by early January 1, raising concerns for transportation disruptions. The Hokuriku region will see mixed rain, snow, and thunderstorms, with risks of lightning and tornadoes. While the Pacific side from Kanto to Kyushu remains mostly clear, it will experience a sharp temperature drop, with cities like Sapporo and Sendai seeing notably colder conditions than the previous day. North winds will intensify the cold sensation. Okinawa will have intermittent rain. The cold will deepen into New Year’s morning, urging thorough cold-weather preparations for events like the first sunrise and shrine visits.
