Twenty-four solar terms and the position of the earth.

A Qingming is the solar term after the vernal equinox, with the time difference of 15 days. The vernal equinox is on March 2 1 day, and the Qingming time is around April 5. The direct point of the sun is located in the northern hemisphere and moves northward, and the sunshine time in the northeast is long, which does not meet the meaning of the question;

Beginning of autumn is the third solar term after the summer solstice, with a time difference of 45 days. The summer solstice is June 22nd, and the autumn begins on August 6th. It's summer now, and the best time to see red leaves in North China is autumn, so it doesn't fit the question.

C beginning of winter is the third solar term after the autumnal equinox, with a time difference of 45 days. The date of the autumnal equinox is September 23rd, and beginning of winter time is165438+1October 7th. The southern coastal areas are still in summer, so it is correct.

D in winter solstice, the height of the noon sun is the smallest in the north of the tropic of cancer, and the highest in the northwest of the year. The great cold is the second solar term after the winter solstice, with a time difference of 1 month, which does not meet the meaning of the question.

So choose: C.