From which poem does "Summer returns to the morning and the night is cool" come?

"Cool in summer and cool at night" comes from "Seven Laws of Twenty-four Solar Terms".

Original "Seven Rhymes of Twenty-four Solar Terms"

The heat is over

When it is cold in summer, the night is cool and the grass is busy.

Red tassels and torches were used to make green curtains, and Guo Jia recruited Songkhla gangs.

Peanuts on the embankment entered the courtyard and corn appeared in front of the village.

When Sichuan glutinous rice is not in a hurry, the goose calls three rounds of labor to put it in storage.

24 solar terms is: beginning of spring, rainy, startled, vernal equinox, Qingming, Grain Rain, Changxia, Xiaoman, Mangzhong, Summer Solstice, Slight Summer, beginning of autumn, Early Summer, White Dew, Autumn Equinox, Cold Dew, Early Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold.

Summer vacation introduction

Summer is the first 14 of the 24 solar terms. The node time is around August 23rd in Gregorian calendar, and the sun arrives at 150. The arrival of the hot summer also means entering the second half of the dry calendar.

The "place" of summer therapy means "termination", and summer therapy means "formal termination of summer heat" Therefore, there is a saying that fighting for summer heat in autumn refers to the time from autumn to summer heat. Although it feels like autumn, the heat in summer has not decreased. Although there is a strong coolness in the morning and evening, the daytime time in Beijing has also been reduced to 13 hours and 25 minutes.