Although winter may seem long and gray, its progress slowly unravels spring. A natural calendar offers reassurance that the coldest days of the year will really and truly lead to warmth. Next week, on January 11, the sun rises earlier for the first time since the middle of June. January 23 is the average date of the midwinter thaw. On January 26: Cardinals begin their spring mating songs, and deep winter ends. On the 28th Average temperatures start to rise one degree per week. On February 1: