How did Zhuge Liang know there would be fog on the water that night?

At that time, Zhuge Liang's soldiers and civilians ate in the barracks every day.

There is a fisherman who delivers fish every day in the camp.

One day, Zhuge Liang found that only his own bowl was full of fish, while others' bowls were full of eels, so he asked the fisherman why.

Fisherman: Because of the recent weather, all the fish swim far away, and eels swim on it because of lack of oxygen in the air, so they are easy to be caught.

So Zhuge Liang listened and asked the fisherman to deliver fish every day, no matter what he caught.

According to whether the fishermen caught fish or eels, they quickly decided when it was foggy.