In ancient times, people always believed that three things would happen during Major Heat: the first thing is the rotten grass turns into fireflies. The second is that the soil becomes wet. The third is that thunder showers happen a lot.

There are about 2000 kinds of fireflies in the world. They are either aquatic or terrestrial. Terrestrial fireflies plant their eggs in the grass. In Major Heat period, the eggs on the grass become baby fireflies. So people in ancient times believed the fireflies transformed from rotten grass. The weather is hot and suffocating in Major Heat, and the soil is wet. Thunder showers happen frequently in Major Heat, which reduces the summer dampness.