The average temperature is around 7.7ºC (46°F) during the day, and 3.8ºC (39°F) at night. It's not as cold as January or February, especially in early December—but it is chilly, so make sure to wear a coat. Gloves, scarves, and hats aren't always necessary, but from mid-December it's a good idea to bring them along.

Tokyo in December is characterized by "crisp and cool" weather rather than "very cold" or freezing temperatures. It is actually one of the sunniest and driest months in the city, with very little rainfall and almost no snow. During the day, temperatures typically reach a high of 12°C (54°F), which is comfortable for walking if you wear a medium-weight coat or a warm sweater. At night, the temperature drops to around 3°C to 5°C (37°F–41°F), which can feel quite chilly due to the low humidity. For most travelers, the weather is perfect for viewing the city's spectacular winter "illuminations" (light displays) or enjoying a hot bowl of ramen. You won't need heavy Arctic gear, but a "layering" strategy is essential: a light thermal base layer, a stylish coat, and a scarf will keep you perfectly comfortable. If you plan to visit the mountains near Tokyo or head north to Hokkaido, you will encounter much harsher winter conditions, but in the metropolitan center, December is generally considered one of the most pleasant times to visit for clear blue skies and festive atmosphere.