Why didn't Zhuge Liang calculate that it would rain in the valley above in Romance of the Three Kingdoms?

In the Romance of the Three Kingdoms, Zhuge Liang is a man of extraordinary wisdom. He took a feather fan and a black scarf and stayed firmly in the army account. With millions of soldiers in his belly, he has the ability to win battles thousands of miles away. We can see that his ingenuity is superb from his borrowing east wind, borrowing arrows from grass boats, and empty city plans, including various exquisite fire plans.

But then again, Zhuge Liang is a mortal, and The Romance of the Three Kingdoms is a romance novel rather than a fairy tale. Therefore, even if Zhuge Liang knows astronomy above and geography below, he can't do everything, and sometimes he miscalculates. Zhuge Liang told Guan Yu to keep Huarong Road and let Cao Cao go. Let Ma Su guard the street pavilion, which is lost. In desperation, Zhuge Liang had to behead Ma Su with tears in his eyes. More seriously, Zhuge Liang had to take great risks and put down an empty plan to scare off Sima Yi's army.

Zhuge Liang was an outstanding astronomer and meteorologist in ancient times. He can predict the future weather according to some changes in nature. For example, borrowing a grass boat with an east wind arrow, he accurately predicted that there would be east wind fog in the next three days, so when Zhou Yu ordered him to build 100,000 arrows in ten days, Zhuge Liang promised to finish the task in three days.

The scene in which Zhuge Liang borrowed the east wind was somewhat magical, as if Zhuge Liang knew magic. In fact, this is Zhuge Liang's mysterious plan to confuse the enemy. Zhuge Liang successfully predicted the weather with his profound meteorological knowledge, so he borrowed an arrow from a Dongfeng grass boat and successfully implemented it.

But Zhuge Liang is actually taking great risks in doing so, because the weather is changeable and Zhuge Liang is also doing probability problems. Everything is easy to do if the prediction is correct, and it is easy to miss the big event once it is not. Success depends on the cooperation between meteorological knowledge and heaven, and the latter is more critical and important. The battle of burning the valley above can be said to be the most typical example that God is not on Zhuge Liang's side. The weather is changeable, and Zhuge Liang was right to predict that it would be fine that day, but it rained cats and dogs in an instant, which was purely an act of god and exceeded the cognitive limit of human beings.

God will not be moved by human will, so when the valley above is full of flames, Sima Yi and his son will die here. After the sudden downpour and the death of Sima and his son, Zhuge Liang, who has always been resourceful, can only sigh: Man proposes, God disposes, and it cannot be strong!

We can't myth Zhuge Liang. Two thousand years ago, in the Three Kingdoms period, technology was backward, and Zhuge Liang was able to predict the weather with his own knowledge, with an accuracy rate of 70% to 80%. Don't say that at that time, even today with advanced technology, our weather forecast is sometimes inaccurate!