禾 + 火 = 秋grain fire

autumn

禾 + 火 = 秋grains fire autumn

  

Autumn is known as the harvest time throughout the Northern Hemisphere. It was the time that the ancient Chinese people would harvest all the grains and then burn the fields to make compost for the next planting cycle. The character for autumn is made by combining the character for grain with fire.

 

The sky is the last character of each of the seasons because the Chinese identified the change of seasons by the changes of the amount of daylight they could see in the sky. 

天

秋天 qiū tiānthe autumn season