noun
winter sun; winter sunshine
Refers to the sun or sunshine during winter, often with a sense of weak, gentle warmth.
冬日が窓から差し込んでいる。
The winter sun is shining in through the window.
noun
below-freezing day; day with sub-zero temperature
Meteorological term for a day when the minimum temperature falls below 0°C. Often used in weather forecasts.
明日は冬日になるでしょう。
Tomorrow will be a below-freezing day.