the middle of the winter

Temperatures can drop well below freezing in midwinter. 仲冬时，温度会大大降低至零度以下。

the winter solstice, the particular day of the year on which it is light for the shortest period of time (21 December in northern parts of the world, 21 June in southern parts of the world)

They celebrate midwinter by lighting candles. 他们点燃蜡烛庆祝冬至。