There is a saying in China
“chūn kùn , qiū fá , xià dǎ dǔn , shuì bú xǐng de dōng sān yuè ”春困，秋乏，夏打盹，睡不醒的冬三月
Spring fever, antumn languor, summer zizz, and always sleepy in winter
Explain that spring is really easy to sleep
As the weather warms, the skin’s capillaries open, a large amount of blood is poured into the capillaries, and the blood content of the corresponding brain and other organs is reduced.
The reason why all people are easy to sleep in the spring.