The weather in a plot is used not just to set the mood, but to foreshadow coming events and symbolize other plot elements. This is important because these changes can be clues to point towards other points that help develop the plot. This helped further develop my ability to evaluate text and find deeper meanings within them.
Geography doesn't just have to change the literal setting; it can also have deeper levels of meaning. For example, geography can be a metaphorical allegory pointing to a real life place, aligning with other possible allegories in the plot for an extended allegory.
The Quest is a very common central plot element, being part of the hero's journey. It is often the middle of the protagonist's motives and actions, and finding examples of these can help a reader quickly and easily decipher a text's meaning.