Why didn't Zhuge Liang consider the weather when he burned Sima in the Three Kingdoms?

This plot is described in the Romance of the Three Kingdoms, but it is not recorded in the official history. But although the novelist said, this plot is not unreasonable: Zhuge Liang attacked Wei in the spring and February of Wei Qinglong's second year (this is true), which was a season when it was warm and cold. When Sima Yi was introduced into the valley, the Shu army ignited the gunpowder buried at the bottom of the valley. When a fire burns, it produces great heat and rises with it. As we all know today, precipitation is caused by the intersection of warm and humid air currents. When the huge heat rising from the valley bottom above reacts violently with the strong cold air over the valley, the sudden rainstorm is natural. Zhuge Liang is not a meteorologist. He knows the general meteorological laws very well, but if he didn't anticipate this special sudden rainfall, it would be impossible to be demanding-of course, Luo Guanzhong still doesn't understand the reason.